Nonlinear Systems of Equations

48 soru

Soru 21Soru

In the xyxy-plane, a circle has center (6,8)(6, 8) and is tangent to the yy-axis. A line with a positive slope mm passes through the origin and is tangent to the circle. If mm is written as a fraction in simplest form, pq\frac{p}{q}, what is the value of p+qp + q?

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Cevap: 31

Cevap

The value of p+qp + q is 31.
The radius of the circle is 6 since the center is (6,8)(6, 8) and it is tangent to the yy-axis. Substituting the line y=mxy = mx into the circle's equation (x6)2+(y8)2=36(x-6)^2 + (y-8)^2 = 36 yields a quadratic equation in xx: (1+m2)x2(12+16m)x+64=0(1+m^2)x^2 - (12+16m)x + 64 = 0. Since the line is tangent to the circle, there is exactly one solution, meaning the discriminant of this quadratic must equal zero: (12+16m)24(1+m2)(64)=0(12+16m)^2 - 4(1+m^2)(64) = 0. Simplifying this equation yields 24m7=024m - 7 = 0, which gives a slope of m=724m = \frac{7}{24}. Since the fraction is in simplest form, p=7p=7 and q=24q=24, and their sum is 3131.

Adım Adım Çözüm

1
Determine the radius of the circle.
r=6r = 6
Since the center is at (6,8)(6, 8) and the circle is tangent to the yy-axis, the radius is the horizontal distance from the center to the yy-axis.
2
Write the equation of the circle.
(x6)2+(y8)2=36(x-6)^2 + (y-8)^2 = 36
A circle with center (h,k)(h, k) and radius rr has the equation (xh)2+(yk)2=r2(x-h)^2 + (y-k)^2 = r^2.
3
Substitute y=mxy = mx into the circle's equation.
(1+m2)x2(12+16m)x+64=0(1+m^2)x^2 - (12+16m)x + 64 = 0
Substituting the equation of the line y=mxy = mx into the circle's equation and expanding gives a quadratic equation in terms of xx.
4
Set the discriminant of the quadratic equation to zero.
Δ=(12+16m)2256(1+m2)=0\Delta = (12+16m)^2 - 256(1+m^2) = 0
For the line to be tangent to the circle, the system must have exactly one real solution, meaning the quadratic equation must have a discriminant of zero.
5
Solve for the positive slope mm.
m=724m = \frac{7}{24}
Expanding and simplifying the discriminant equation yields 24m7=024m - 7 = 0, which gives m=724m = \frac{7}{24}.
6
Calculate p+qp + q using the simplest form fraction.
3131
Since m=724m = \frac{7}{24} is in simplest form, p=7p = 7 and q=24q = 24. Therefore, p+q=7+24=31p + q = 7 + 24 = 31.

Anahtar Kavram

Nonlinear Systems of Equations
Soru 22Soru

For a real solution (x,y)(x, y) to the system of equations below, which of the following is a possible value of x+yx + y?

x2+3y2=21x22y=5\begin{aligned} x^2 + 3y^2 &= 21 \\ x^2 - 2y &= 5 \end{aligned}
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Cevap: 5

Cevap

The correct answer is 5, which is the sum of the coordinates of the real solution (3, 2) of the system.
Substituting x2=2y+5x^2 = 2y + 5 into the first equation yields the quadratic equation 3y2+2y16=03y^2 + 2y - 16 = 0. Solving this quadratic equation gives y=2y = 2 or y=8/3y = -8/3. Since x2x^2 must be non-negative for real solutions, y=8/3y = -8/3 yields no real solutions because x2=2(8/3)+5=1/3<0x^2 = 2(-8/3) + 5 = -1/3 < 0. For y=2y = 2, we have x2=2(2)+5=9x^2 = 2(2) + 5 = 9, which gives x=3x = 3 or x=3x = -3. The real solutions to the system are (3,2)(3, 2) and (3,2)(-3, 2). The possible values for x+yx + y are 3+2=53 + 2 = 5 and 3+2=1-3 + 2 = -1. Therefore, 5 is a possible value of x+yx + y.

Adım Adım Çözüm

1
Rearrange the second equation to express x2x^2 in terms of yy.
x2=2y+5x^2 = 2y + 5
This allows for direct substitution into the first equation to eliminate the xx variable.
2
Substitute the expression for x2x^2 into the first equation and simplify the resulting quadratic equation in terms of yy.
3y2+2y16=03y^2 + 2y - 16 = 0
Substituting 2y+52y + 5 for x2x^2 in x2+3y2=21x^2 + 3y^2 = 21 gives (2y+5)+3y2=21(2y + 5) + 3y^2 = 21, which simplifies to 3y2+2y16=03y^2 + 2y - 16 = 0.
3
Factor or use the quadratic formula to solve for yy.
y=2y = 2 or y=8/3y = -8/3
The quadratic equation factors as (3y+8)(y2)=0(3y + 8)(y - 2) = 0, giving the roots y=2y = 2 and y=8/3y = -8/3.
4
Find the corresponding values of xx for each yy and determine the real solutions.
For y=2y = 2, x2=2(2)+5=9    x=±3x^2 = 2(2) + 5 = 9 \implies x = \pm 3. For y=8/3y = -8/3, x2=2(8/3)+5=1/3x^2 = 2(-8/3) + 5 = -1/3, which has no real solutions.
A real number squared cannot be negative, so only y=2y = 2 yields real solutions: (3,2)(3, 2) and (3,2)(-3, 2).
5
Calculate the possible values of x+yx + y for the real solutions.
For (3,2)(3, 2), x+y=3+2=5x + y = 3 + 2 = 5. For (3,2)(-3, 2), x+y=3+2=1x + y = -3 + 2 = -1.
Evaluating the target expression for both valid real solutions gives 5 and -1. Since 5 is the only value present in the options, it is the correct answer.

Anahtar Kavram

Solving systems of nonlinear equations algebraically using substitution and analyzing real solutions.
Soru 23Soru

A system of two equations is given:

y=x2+kx+4y = x^2 + kx + 4
y=4xky = 4x - k

In these equations, kk represents a positive constant. If the system has a single real solution, what is the value of kk?

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Cevap: 12

Cevap

12
Setting the two equations equal yields the quadratic equation x2+(k4)x+(k+4)=0x^2 + (k - 4)x + (k + 4) = 0. For the system to have exactly one real solution, the discriminant of this quadratic equation must be equal to 00. The discriminant is (k4)24(1)(k+4)=k212k(k - 4)^2 - 4(1)(k + 4) = k^2 - 12k. Solving k212k=0k^2 - 12k = 0 yields k=0k = 0 or k=12k = 12. Since kk must be positive, the value of kk is 1212.

Adım Adım Çözüm

1
Set the two equations equal to each other to form a single quadratic equation in terms of xx.
x2+(k4)x+(k+4)=0x^2 + (k - 4)x + (k + 4) = 0
Equating the expressions for yy allows us to find the xx-coordinates where the graphs of the two equations intersect.
2
Set the discriminant of the quadratic equation to zero.
(k4)24(1)(k+4)=0(k - 4)^2 - 4(1)(k + 4) = 0
A system of equations consisting of a line and a parabola has a single real solution if and only if the line is tangent to the parabola, which corresponds to a quadratic equation with a discriminant of zero.
3
Expand and simplify the equation for kk.
k212k=0k^2 - 12k = 0
Expanding (k4)2(k - 4)^2 yields k28k+16k^2 - 8k + 16, and distributing 4-4 yields 4k16-4k - 16. Combining like terms simplifies the relation.
4
Solve for kk and apply the constraint that k>0k > 0.
k=12k = 12
Factoring k(k12)=0k(k - 12) = 0 gives k=0k = 0 or k=12k = 12. Since kk is specified to be positive, k=12k = 12 is the correct value.

Anahtar Kavram

Solving nonlinear systems of equations by substitution and using the discriminant to find conditions for a single real solution.
Soru 24Soru

If (x,y)(x, y) is a solution to the system of equations below and x>0x > 0, what is the value of x+yx + y?

x2+y2=50xy=6\begin{aligned} x^2 + y^2 &= 50 \\ x - y &= 6 \end{aligned}
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Cevap: 8

Cevap

8
Solving the linear equation for xx gives x=y+6x = y + 6. Substituting this into the circle equation yields (y+6)2+y2=50(y + 6)^2 + y^2 = 50, which simplifies to 2y2+12y14=02y^2 + 12y - 14 = 0. Dividing by 22 gives y2+6y7=0y^2 + 6y - 7 = 0, which factors as (y+7)(y1)=0(y + 7)(y - 1) = 0. This yields y=1y = 1 (with x=7x = 7) or y=7y = -7 (with x=1x = -1). The constraint x>0x > 0 requires selecting the solution (7,1)(7, 1). The sum of xx and yy for this solution is 7+1=87 + 1 = 8.

Adım Adım Çözüm

1
Express xx in terms of yy using the linear equation.
x=y+6x = y + 6
This allows for substitution into the second equation to reduce the system to a single variable.
2
Substitute the expression for xx into the equation of the circle and expand.
2y2+12y14=02y^2 + 12y - 14 = 0
Substituting x=y+6x = y + 6 into x2+y2=50x^2 + y^2 = 50 yields (y+6)2+y2=50(y + 6)^2 + y^2 = 50. Expanding gives y2+12y+36+y2=50y^2 + 12y + 36 + y^2 = 50.
3
Simplify and solve the quadratic equation by factoring.
y=1y = 1 or y=7y = -7
Dividing the equation by 2 gives y2+6y7=0y^2 + 6y - 7 = 0, which factors as (y+7)(y1)=0(y + 7)(y - 1) = 0.
4
Calculate the corresponding values of xx for each yy.
For y=1y = 1, x=7x = 7; for y=7y = -7, x=1x = -1
Using the relation x=y+6x = y + 6 yields the coordinates of the two intersection points.
5
Apply the constraint x>0x > 0 and calculate x+yx + y.
x+y=8x + y = 8
Since x>0x > 0, the only valid solution is (7,1)(7, 1). The sum of the coordinates is 7+1=87 + 1 = 8.

Anahtar Kavram

Solving a nonlinear system of equations representing a circle and a line using substitution and factoring.
Soru 25Soru

In the xyxy-plane, the graphs of the linear function 3x+y=63x + y = 6 and the quadratic function y=3x25x2y = 3x^2 - 5x - 2 intersect at two points. What is the sum of the yy-coordinates of these two intersection points?

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Cevap: 10

Cevap

10
The correct answer is 10. By rewriting the linear equation as y=63xy = 6 - 3x and substituting it into the quadratic equation, we get 63x=3x25x26 - 3x = 3x^2 - 5x - 2. Collecting all terms on one side yields the quadratic equation 3x22x8=03x^2 - 2x - 8 = 0. Factoring this equation gives (3x+4)(x2)=0(3x + 4)(x - 2) = 0, which results in x=2x = 2 and x=43x = -\frac{4}{3}. Substituting these xx-values back into the linear equation gives the yy-coordinates: y=63(2)=0y = 6 - 3(2) = 0 and y=63(43)=10y = 6 - 3(-\frac{4}{3}) = 10. The sum of these yy-coordinates is 0+10=100 + 10 = 10.

Adım Adım Çözüm

1
Express yy in terms of xx using the linear equation.
y=63xy = 6 - 3x
Isolating yy makes substitution into the quadratic equation straightforward.
2
Substitute the expression for yy into the quadratic equation and set the equation to zero.
63x=3x25x26 - 3x = 3x^2 - 5x - 2, which simplifies to 3x22x8=03x^2 - 2x - 8 = 0.
This forms a single quadratic equation in terms of xx to find the xx-coordinates of the intersection points.
3
Solve the quadratic equation by factoring.
(3x+4)(x2)=0(3x + 4)(x - 2) = 0, yielding x=2x = 2 and x=43x = -\frac{4}{3}.
Factoring determines the values of xx at the points of intersection.
4
Substitute the xx-values back into the linear equation y=63xy = 6 - 3x to find the corresponding yy-coordinates.
For x=2x = 2: y=63(2)=0y = 6 - 3(2) = 0. For x=43x = -\frac{4}{3}: y=63(43)=10y = 6 - 3(-\frac{4}{3}) = 10.
This identifies the coordinates of the two intersection points as (2,0)(2, 0) and (43,10)(-\frac{4}{3}, 10).
5
Calculate the sum of the yy-coordinates.
0+10=100 + 10 = 10
The question asks for the sum of the yy-coordinates of the two intersection points.

Anahtar Kavram

Solving a system of linear and quadratic equations using substitution.
Tahmini Süre:1m 30s
Soru 26Soru

In the xyxy-plane, the graphs of the linear equation y=3x+ky = 3x + k, where kk is a constant, and the quadratic equation y=x22x+7y = x^2 - 2x + 7 intersect at two points. If the distance between the two points of intersection is 130\sqrt{130}, what is the value of kk?

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Cevap: 4

Cevap

4
The correct value of kk is 44. Equating the two equations yields the quadratic equation x25x+(7k)=0x^2 - 5x + (7 - k) = 0. Since the slope of the line is 33, the difference in the y-coordinates of the intersection points is 33 times the difference in the x-coordinates. Applying the distance formula shows that the distance is equal to 10(x2x1)2\sqrt{10(x_2 - x_1)^2}. Setting this equal to the given distance of 130\sqrt{130} yields (x2x1)2=13(x_2 - x_1)^2 = 13. Substituting Vieta's relations (x1+x2=5x_1 + x_2 = 5 and x1x2=7kx_1 x_2 = 7 - k) into the identity (x2x1)2=(x1+x2)24x1x2(x_2 - x_1)^2 = (x_1 + x_2)^2 - 4x_1 x_2 results in 13=254(7k)13 = 25 - 4(7 - k), which simplifies to k=4k = 4.

Adım Adım Çözüm

1
Equate the linear and quadratic equations to set up the intersection condition.
x22x+7=3x+k    x25x+(7k)=0x^2 - 2x + 7 = 3x + k \dots \implies x^2 - 5x + (7 - k) = 0
The x-coordinates of the intersection points are the roots of this quadratic equation.
2
Express the distance between the two points (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) in terms of the difference of their x-coordinates.
d=(x2x1)2+(y2y1)2=(x2x1)2+(3(x2x1))2=10(x2x1)2d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} = \sqrt{(x_2 - x_1)^2 + (3(x_2 - x_1))^2} = \sqrt{10(x_2 - x_1)^2}
Since both points lie on the line y=3x+ky = 3x + k, the difference in their y-coordinates is y2y1=3(x2x1)y_2 - y_1 = 3(x_2 - x_1).
3
Use the given distance to find the value of (x2x1)2(x_2 - x_1)^2.
10(x2x1)2=130    (x2x1)2=1310(x_2 - x_1)^2 = 130 \implies (x_2 - x_1)^2 = 13
The distance between the intersection points is given as 130\sqrt{130}.
4
Apply Vieta's formulas and the algebraic identity for the squared difference of the roots to solve for kk.
x1+x2=5x_1 + x_2 = 5 and x1x2=7kx_1 x_2 = 7 - k. Substituting these into (x2x1)2=(x1+x2)24x1x2(x_2 - x_1)^2 = (x_1 + x_2)^2 - 4x_1 x_2 gives 13=524(7k)    13=2528+4k    4k=16    k=413 = 5^2 - 4(7 - k) \implies 13 = 25 - 28 + 4k \implies 4k = 16 \implies k = 4.
Vieta's formulas relate the coefficients of the quadratic equation to the sum and product of its roots.

Anahtar Kavram

Solving systems of linear and quadratic equations and finding constants based on geometric constraints.
Soru 27Soru

In the system of equations below, kk is a constant.

y=3x212x+7y=kx5\begin{aligned} y &= 3x^2 - 12x + 7 \\ y &= kx - 5 \end{aligned}

If the system has two distinct real solutions, (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2), such that the average of the xx-coordinates of the solutions is 33, what is the value of kk?

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Cevap: 6

Cevap

6
To find the value of kk, we set the two equations equal to each other to solve for the xx-coordinates of the intersection points: 3x212x+7=kx53x^2 - 12x + 7 = kx - 5. Moving all terms to one side gives the quadratic equation 3x2(12+k)x+12=03x^2 - (12+k)x + 12 = 0. The sum of the roots x1+x2x_1 + x_2 is given by ba=12+k3-\frac{b}{a} = \frac{12+k}{3}. The average of the roots is x1+x22=12+k6\frac{x_1 + x_2}{2} = \frac{12+k}{6}. Since the average of the xx-coordinates is 33, we set 12+k6=3\frac{12+k}{6} = 3, which gives 12+k=1812+k = 18, and solving for kk yields 66. Evaluating the discriminant with k=6k = 6 gives (18)24(3)(12)=324144=180>0(-18)^2 - 4(3)(12) = 324 - 144 = 180 > 0, confirming two distinct real solutions.

Adım Adım Çözüm

1
Equate the two equations to find the xx-coordinates of the intersection points.
3x212x+7=kx53x^2 - 12x + 7 = kx - 5
The intersection points of the system occur where the yy-values of the two functions are equal.
2
Rearrange the equation into standard quadratic form: ax2+bx+c=0ax^2 + bx + c = 0.
3x2(12+k)x+12=03x^2 - (12+k)x + 12 = 0
Grouping the like terms allows us to identify the quadratic coefficients a=3a = 3, b=(12+k)b = -(12+k), and c=12c = 12.
3
Express the sum and the average of the solutions in terms of kk using Vieta's formulas.
Sum of solutions x1+x2=ba=12+k3x_1 + x_2 = -\frac{b}{a} = \frac{12+k}{3}, so the average is x1+x22=12+k6\frac{x_1 + x_2}{2} = \frac{12+k}{6}.
Vieta's formulas state that the sum of the roots of a quadratic equation is ba-\frac{b}{a}. The average is half of the sum.
4
Set the average equal to 33 and solve for kk.
12+k6=3    12+k=18    k=6\frac{12+k}{6} = 3 \implies 12+k = 18 \implies k = 6.
The problem states that the average of the xx-coordinates of the solutions is 33.
5
Verify that k=6k = 6 yields two distinct real solutions by checking the discriminant.
For k=6k = 6, the equation is 3x218x+12=03x^2 - 18x + 12 = 0. The discriminant is D=(18)24(3)(12)=324144=180D = (-18)^2 - 4(3)(12) = 324 - 144 = 180. Since D>0D > 0, two distinct real solutions exist.
A positive discriminant ensures that there are two distinct real solutions, satisfying the problem's condition.

Anahtar Kavram

Solving nonlinear systems of equations using quadratic properties and Vieta's formulas.
Soru 28Soru

For a constant kk, the circle (x5)2+(y5)2=18(x - 5)^2 + (y - 5)^2 = 18 and the line y=kxy = kx are graphed in the xyxy-plane. For how many integer values of kk will the circle and the line intersect at exactly two points?

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Cevap: 6

Cevap

6
The correct answer is 6. By substituting the line equation y=kxy = kx into the circle equation, we obtain the quadratic equation (k2+1)x210(k+1)x+32=0(k^2 + 1)x^2 - 10(k + 1)x + 32 = 0. For the circle and line to intersect at exactly two points, this equation must have two distinct real roots, meaning its discriminant must be positive. This leads to the inequality 7k250k+7<07k^2 - 50k + 7 < 0, which factors as (7k1)(k7)<0(7k - 1)(k - 7) < 0. The solution is the interval 17<k<7\frac{1}{7} < k < 7. The integer values of kk in this range are 1,2,3,4,5,1, 2, 3, 4, 5, and 66, giving a total of 6 integers.

Adım Adım Çözüm

1
Substitute the line equation y=kxy = kx into the circle equation (x5)2+(y5)2=18(x - 5)^2 + (y - 5)^2 = 18.
(x5)2+(kx5)2=18(x - 5)^2 + (kx - 5)^2 = 18
Substitution reduces the system of equations to a single quadratic equation in xx, representing the xx-coordinates of the intersection points.
2
Expand the terms and write the equation in standard quadratic form Ax2+Bx+C=0Ax^2 + Bx + C = 0.
(k2+1)x210(k+1)x+32=0(k^2 + 1)x^2 - 10(k + 1)x + 32 = 0
Putting the equation in standard form is necessary to analyze its discriminant.
3
Set the discriminant Δ=b24ac\Delta = b^2 - 4ac strictly greater than zero to ensure exactly two distinct real solutions.
[10(k+1)]24(k2+1)(32)>07k250k+7<0[-10(k+1)]^2 - 4(k^2 + 1)(32) > 0 \Rightarrow 7k^2 - 50k + 7 < 0
A quadratic equation has two distinct real roots if and only if its discriminant is positive.
4
Solve the quadratic inequality 7k250k+7<07k^2 - 50k + 7 < 0 by factoring the quadratic expression.
17<k<7\frac{1}{7} < k < 7
The roots of (7k1)(k7)=0(7k - 1)(k - 7) = 0 are k=17k = \frac{1}{7} and k=7k = 7. Since the leading coefficient is positive, the expression is negative between these roots.
5
Identify and count the integer values of kk that lie within the interval (17,7)(\frac{1}{7}, 7).
The integers are 1,2,3,4,5,61, 2, 3, 4, 5, 6, which gives a total of 6 values.
The integers that are strictly greater than 17\frac{1}{7} and strictly less than 77 are the whole numbers from 11 to 66.

Anahtar Kavram

Solving systems consisting of a circle and a line algebraically by utilizing the quadratic discriminant to find the condition for two real intersection points.
Soru 29Soru
The system of equations below consists of a linear equation and a quadratic equation:
y2x=5y=x23x1\begin{aligned} y - 2x &= 5 \\ y &= x^2 - 3x - 1 \end{aligned}
Let (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) represent the two distinct real coordinate points where the graphs of these equations intersect. If y1>y2y_1 > y_2, what is the value of x1x2x_1 - x_2?
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Cevap: 7

Cevap

7
Solving the system algebraically by expressing yy as 2x+52x + 5 and substituting it into the quadratic equation leads to x25x6=0x^2 - 5x - 6 = 0. Factoring this equation yields x=6x = 6 and x=1x = -1. Evaluating these values in the linear equation gives the coordinates (6,17)(6, 17) and (1,3)(-1, 3). Since 17>317 > 3, the point (6,17)(6, 17) corresponds to (x1,y1)(x_1, y_1) and (1,3)(-1, 3) corresponds to (x2,y2)(x_2, y_2). The difference x1x2x_1 - x_2 is equal to 6(1)=76 - (-1) = 7.

Adım Adım Çözüm

1
Solve for yy in the linear equation to express it in terms of xx.
y=2x+5y = 2x + 5
This allows for substitution into the quadratic equation to eliminate one variable.
2
Substitute 2x+52x + 5 for yy in the quadratic equation.
2x+5=x23x12x + 5 = x^2 - 3x - 1
To create a single-variable quadratic equation in terms of xx.
3
Rearrange the equation by subtracting 2x2x and 55 from both sides to set it equal to zero.
x25x6=0x^2 - 5x - 6 = 0
Setting the quadratic equation to zero is the standard first step to find its roots.
4
Factor the quadratic trinomial.
(x6)(x+1)=0(x - 6)(x + 1) = 0, which gives x=6x = 6 and x=1x = -1.
Factoring finds the xx-coordinates of the points of intersection.
5
Substitute the xx-values back into the linear equation y=2x+5y = 2x + 5 to determine the corresponding yy-values.
For x=6x = 6, y=2(6)+5=17y = 2(6) + 5 = 17. For x=1x = -1, y=2(1)+5=3y = 2(-1) + 5 = 3. The intersection points are (6,17)(6, 17) and (1,3)(-1, 3).
This defines the full coordinate pairs of the system's solutions.
6
Apply the condition y1>y2y_1 > y_2 to identify (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2).
Since 17>317 > 3, the first solution is (x1,y1)=(6,17)(x_1, y_1) = (6, 17) and the second solution is (x2,y2)=(1,3)(x_2, y_2) = (-1, 3).
This aligns the coordinate values with the variables defined in the problem constraint.
7
Calculate the value of x1x2x_1 - x_2.
6(1)=76 - (-1) = 7
Subtracting a negative value is equivalent to adding its absolute value, yielding the final required answer.

Anahtar Kavram

Nonlinear Systems of Equations
Soru 30Soru
In the system of equations below, kk is a constant.
x2+y2+8y=9x2+y=k\begin{aligned} x^2 + y^2 + 8y &= 9 \\ x^2 + y &= k \end{aligned}
If the system has exactly 3 distinct real solutions (x,y)(x, y), what is the value of kk?
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Cevap: 1

Cevap

The value of kk is 1.
Substituting x2=kyx^2 = k - y into x2+y2+8y=9x^2 + y^2 + 8y = 9 gives y2+7y+k9=0y^2 + 7y + k - 9 = 0. For the system to have exactly 3 distinct real solutions, the vertex of the parabola y=x2+ky = -x^2 + k must lie on the circle, which corresponds to the root y=ky = k. Substituting y=ky = k into the quadratic equation yields k2+8k9=0k^2 + 8k - 9 = 0, which gives k=1k = 1 or k=9k = -9. For k=1k = 1, the roots of the quadratic are y=1y = 1 and y=8y = -8. The root y=1y = 1 yields 1 real solution, (0,1)(0, 1), and the root y=8y = -8 yields 2 real solutions, (3,8)(3, -8) and (3,8)(-3, -8), for a total of 3 real solutions. For k=9k = -9, the roots are y=9y = -9 and y=2y = 2. The root y=2y = 2 does not yield any real solutions for xx because 2>92 > -9, so the system has only 1 real solution. Thus, k=1k = 1.

Adım Adım Çözüm

1
Express x2x^2 in terms of yy and kk from the second equation.
x2=kyx^2 = k - y (with constraint yky \le k for real xx)
To prepare for substitution into the first equation and establish the boundary condition for real solutions.
2
Substitute x2=kyx^2 = k - y into the first equation.
y2+7y+k9=0y^2 + 7y + k - 9 = 0
To create a single quadratic equation in terms of yy.
3
Analyze the conditions on the roots of the quadratic equation to get exactly 3 distinct real solutions.
One root must equal kk and the other must be less than kk.
A root y=ky = k yields 1 real solution for xx (x=0x = 0), while a root y<ky < k yields 2 real solutions (x=±kyx = \pm\sqrt{k-y}).
4
Find the candidate values of kk by setting y=ky = k in the quadratic equation.
k2+8k9=0    k=1k^2 + 8k - 9 = 0 \implies k = 1 or k=9k = -9
To find the values of kk where the parabola's vertex lies on the circle.
5
Verify which candidate value of kk satisfies all conditions.
For k=1k = 1, the roots are y=1y = 1 and y=8<1y = -8 < 1 (3 solutions). For k=9k = -9, the roots are y=9y = -9 and y=2>9y = 2 > -9 (1 solution). Therefore, k=1k = 1.
To ensure the second root is strictly less than kk, guaranteeing exactly 3 solutions.

Anahtar Kavram

Analyzing the number of solutions in a nonlinear system of equations using algebraic substitution and boundary constraints.
Tahmini Süre:3m 0s
Soru 31Soru

In the xyxy-plane, the graph of the linear equation 3x+4y=k3x + 4y = k, where kk is a positive constant, is tangent to the circle with equation x2+y22x4y=20x^2 + y^2 - 2x - 4y = 20. What is the value of kk?

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Cevap: 36

Cevap

The value of the constant kk is 3636.
To find the value of kk where the line 3x+4y=k3x + 4y = k is tangent to the circle, we first rewrite the circle's equation x2+y22x4y=20x^2 + y^2 - 2x - 4y = 20 in standard form by completing the square: (x22x+1)+(y24y+4)=20+1+4(x^2 - 2x + 1) + (y^2 - 4y + 4) = 20 + 1 + 4, which simplifies to (x1)2+(y2)2=25(x - 1)^2 + (y - 2)^2 = 25. This is a circle centered at (1,2)(1, 2) with a radius of 55. A line is tangent to a circle if the perpendicular distance from the center of the circle to the line is equal to the radius of the circle. Using the distance formula Ax0+By0CA2+B2\frac{|Ax_0 + By_0 - C|}{\sqrt{A^2 + B^2}} for the point (1,2)(1, 2) and the line 3x+4yk=03x + 4y - k = 0, we set up the equation: 3(1)+4(2)k32+42=5\frac{|3(1) + 4(2) - k|}{\sqrt{3^2 + 4^2}} = 5. This simplifies to 11k5=5\frac{|11 - k|}{5} = 5, or 11k=25|11 - k| = 25. Solving the absolute value equation gives 11k=25k=1411 - k = 25 \Rightarrow k = -14 and 11k=25k=3611 - k = -25 \Rightarrow k = 36. Since the problem specifies that kk is a positive constant, the correct answer is 3636.

Adım Adım Çözüm

1
Rewrite the circle's equation by completing the square for both variables.
(x1)2+(y2)2=25(x - 1)^2 + (y - 2)^2 = 25
To identify the center and radius of the circle.
2
Identify the center and radius from the standard form of the circle's equation.
Center is (1,2)(1, 2) and radius is 55.
The standard form of a circle is (xh)2+(yk)2=r2(x-h)^2 + (y-k)^2 = r^2.
3
Apply the condition for tangency: the perpendicular distance from the center (1,2)(1, 2) to the line 3x+4yk=03x + 4y - k = 0 must equal the radius 55.
3(1)+4(2)k32+42=5\frac{|3(1) + 4(2) - k|}{\sqrt{3^2 + 4^2}} = 5
A line is tangent to a circle if and only if the distance from the center to the line equals the radius.
4
Simplify the distance equation and solve the resulting absolute value equation for kk.
11k=25|11 - k| = 25, yielding k=14k = -14 or k=36k = 36.
To find all mathematically possible values of the constant kk.
5
Select the positive value for kk as specified by the problem constraints.
k=36k = 36
The problem states that kk is a positive constant.

Anahtar Kavram

The relationship between a line and a circle in a nonlinear system, specifically using the distance from the center to a tangent line to solve for an unknown constant.
Soru 32Soru

A circle in the xyxy-plane is defined by the equation (x3)2+(y2)2=13(x - 3)^2 + (y - 2)^2 = 13. The line y=3xy = 3x intersects the circle at the origin (0,0)(0, 0) and at a second point PP. What is the yy-coordinate of point PP?

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Cevap: 275\frac{27}{5}

Cevap

The y-coordinate of point P is 275\frac{27}{5}.
Substituting the linear relationship y=3xy = 3x into the circle equation yields a quadratic equation in terms of xx. Solving this equation gives the xx-coordinates of the intersection points as x=0x = 0 and x=95x = \frac{9}{5}. Since point PP is not the origin, its xx-coordinate is 95\frac{9}{5}. Substituting this back into y=3xy = 3x gives the yy-coordinate of point PP as 275\frac{27}{5}.

Adım Adım Çözüm

1
Substitute the linear equation y=3xy = 3x into the equation of the circle.
(x3)2+(3x2)2=13(x - 3)^2 + (3x - 2)^2 = 13
Substitution reduces the system of two equations with two variables to a single quadratic equation with one variable.
2
Expand and simplify the equation.
10x218x=010x^2 - 18x = 0
Expanding (x3)2(x - 3)^2 to x26x+9x^2 - 6x + 9 and (3x2)2(3x - 2)^2 to 9x212x+49x^2 - 12x + 4, then combining like terms and subtracting 13 from both sides, isolates the quadratic terms.
3
Solve for xx by factoring.
2x(5x9)=02x(5x - 9) = 0, which gives x=0x = 0 or x=95x = \frac{9}{5}.
The roots of the factored equation represent the x-coordinates of the two intersection points.
4
Find the y-coordinate of the second point PP using y=3xy = 3x.
y=3(95)=275y = 3 \left(\frac{9}{5}\right) = \frac{27}{5}
Since point PP is not the origin, its x-coordinate must be 95\frac{9}{5}. Substituting this into the linear equation gives its corresponding y-coordinate.

Anahtar Kavram

Solving nonlinear systems of equations involving a circle and a line by substitution.
Soru 33Soru
y=x2x72xy=3\begin{aligned} y &= x^2 - x - 7 \\ 2x - y &= -3 \end{aligned}

If (x,y)(x, y) is a solution to the system of equations above and x<0x < 0, what is the value of x+yx + y?

Cevabı ve açıklamayı göster

Cevap: -3

Cevap

The correct answer is -3.
The correct answer is 3-3. To find this, substitute the expression for yy from the first equation into the second equation, which yields 2x(x2x7)=32x - (x^2 - x - 7) = -3. Distributing the negative sign and combining like terms gives x2+3x+7=3-x^2 + 3x + 7 = -3. Setting the equation to zero results in x23x10=0x^2 - 3x - 10 = 0. Factoring the quadratic expression gives (x5)(x+2)=0(x - 5)(x + 2) = 0, which means x=5x = 5 or x=2x = -2. Since the question specifies that x<0x < 0, we select x=2x = -2. Substituting x=2x = -2 back into the linear equation gives y=2(2)+3=1y = 2(-2) + 3 = -1. Finally, calculating x+yx + y gives 2+(1)=3-2 + (-1) = -3.

Adım Adım Çözüm

1
Substitute the expression for yy from the first equation into the second equation.
2x(x2x7)=32x - (x^2 - x - 7) = -3
This allows us to eliminate yy and solve for xx in a single variable quadratic equation.
2
Distribute the negative sign and simplify the equation.
x2+3x+7=3-x^2 + 3x + 7 = -3
Expanding the parentheses correctly preserves the signs of the quadratic terms.
3
Rearrange the terms to set the quadratic equation to zero.
x23x10=0x^2 - 3x - 10 = 0
Writing the equation in standard form (ax2+bx+c=0ax^2 + bx + c = 0) allows us to factor it.
4
Factor the quadratic expression.
(x5)(x+2)=0(x - 5)(x + 2) = 0
Finding factors that multiply to 10-10 and add to 3-3 gives us the solutions for xx.
5
Solve for xx and apply the constraint x<0x < 0.
x=2x = -2
The equation yields x=5x = 5 or x=2x = -2. The constraint x<0x < 0 means we must choose x=2x = -2.
6
Substitute x=2x = -2 back into one of the original equations to solve for yy.
y=2(2)+3=1y = 2(-2) + 3 = -1
We need the corresponding yy-value to find the value of x+yx + y.
7
Calculate the value of x+yx + y.
x+y=2+(1)=3x + y = -2 + (-1) = -3
This provides the final required value specified in the question.

Anahtar Kavram

Solving a system of one linear equation and one quadratic equation using substitution.
Soru 34Soru
xy=3y=x27x+12\begin{aligned} x - y &= 3 \\ y &= x^2 - 7x + 12 \end{aligned}

If (x,y)(x, y) is a solution to the system of equations above and y>0y > 0, what is the value of xyxy?

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Cevap: 10

Cevap

10
By substituting the linear equation y=x3y = x - 3 into the quadratic equation, we obtain a single quadratic equation x28x+15=0x^2 - 8x + 15 = 0. Factoring this equation yields the solutions x=3x = 3 and x=5x = 5. The corresponding yy-coordinates are y=0y = 0 and y=2y = 2, respectively. Since the problem specifies that y>0y > 0, we choose the solution (5,2)(5, 2). The product of the coordinates is 52=105 \cdot 2 = 10.

Adım Adım Çözüm

1
Express yy in terms of xx from the linear equation.
y=x3y = x - 3
This allows for substitution into the second equation.
2
Substitute y=x3y = x - 3 into the quadratic equation.
x3=x27x+12x - 3 = x^2 - 7x + 12
To create a single quadratic equation in terms of xx.
3
Rearrange the equation into standard quadratic form ax2+bx+c=0ax^2 + bx + c = 0.
x28x+15=0x^2 - 8x + 15 = 0
Subtracting xx and adding 33 to both sides enables factoring.
4
Factor the quadratic expression.
(x3)(x5)=0(x - 3)(x - 5) = 0
To find the roots of the equation, which are x=3x = 3 and x=5x = 5.
5
Find the corresponding yy-values for each xx-value.
For x=3x = 3, y=33=0y = 3 - 3 = 0. For x=5x = 5, y=53=2y = 5 - 3 = 2.
To obtain the complete coordinate pairs of the intersection points.
6
Apply the constraint y>0y > 0 to select the correct solution pair.
The solution (5,2)(5, 2) is selected since its yy-coordinate is greater than 00.
The other solution, (3,0)(3, 0), has y=0y = 0, which does not satisfy the constraint y>0y > 0.
7
Calculate the value of xyxy for the chosen solution.
xy=52=10xy = 5 \cdot 2 = 10
To find the final requested value.

Anahtar Kavram

Solving a nonlinear system of equations containing a linear equation and a quadratic equation by substitution.
Tahmini Süre:1m 30s
Soru 35Soru
(x4)2+(y+1)2=18x+y=k\begin{aligned} (x - 4)^2 + (y + 1)^2 &= 18 \\ x + y &= k \end{aligned}

In the system of equations above, kk is a constant. If the system has exactly one real solution, what is the sum of all possible values of kk?

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Cevap: 6

Cevap

The sum of all possible values of kk is 66.
The system of equations has exactly one real solution when the line is tangent to the circle. The circle (x4)2+(y+1)2=18(x - 4)^2 + (y + 1)^2 = 18 has center (4,1)(4, -1) and radius 18=32\sqrt{18} = 3\sqrt{2}. The distance from the center of the circle to the line x+yk=0x + y - k = 0 is given by 41k12+12=3k2\frac{|4 - 1 - k|}{\sqrt{1^2 + 1^2}} = \frac{|3 - k|}{\sqrt{2}}. Setting this distance equal to the radius yields 3k2=32    3k=6\frac{|3 - k|}{\sqrt{2}} = 3\sqrt{2} \implies |3 - k| = 6. Solving this equation gives k=9k = 9 and k=3k = -3. The sum of these possible values is 9+(3)=69 + (-3) = 6.

Adım Adım Çözüm

1
Relate the algebraic condition of having exactly one solution to the geometric relationship between the circle and the line.
The line must be tangent to the circle, meaning the perpendicular distance from the center of the circle to the line must equal the radius of the circle.
A system consisting of a circle and a line has exactly one real solution if and only if the line is tangent to the circle.
2
Identify the center and radius of the circle from the equation (x4)2+(y+1)2=18(x - 4)^2 + (y + 1)^2 = 18.
The center of the circle is (4,1)(4, -1) and the radius is r=18=32r = \sqrt{18} = 3\sqrt{2}.
The standard form of a circle equation is (xh)2+(yk)2=r2(x - h)^2 + (y - k)^2 = r^2, where (h,k)(h, k) is the center and rr is the radius.
3
Express the line equation in standard form Ax+By+C=0Ax + By + C = 0 and set up the perpendicular distance formula.
The line equation is x+yk=0x + y - k = 0. The distance from the center (4,1)(4, -1) to the line is d=(1)(4)+(1)(1)k12+12=3k2d = \frac{|(1)(4) + (1)(-1) - k|}{\sqrt{1^2 + 1^2}} = \frac{|3 - k|}{\sqrt{2}}.
The perpendicular distance from a point (x0,y0)(x_0, y_0) to a line Ax+By+C=0Ax + By + C = 0 is given by d=Ax0+By0+CA2+B2d = \frac{|Ax_0 + By_0 + C|}{\sqrt{A^2 + B^2}}.
4
Set the distance equal to the radius of the circle and solve the absolute value equation for kk.
\frac{|3 - k|}{\sqrt{2}} = 3\sqrt{2} \implies |3 - k| = 6 .Thisyieldstwoequations:. This yields two equations: 3 - k = 6 \implies k = -3 ,and, and 3 - k = -6 \implies k = 9$.
Setting the distance equal to the radius ensures that the line is tangent to the circle, resulting in exactly one point of intersection.
5
Calculate the sum of all possible values of kk.
Sum = 3+9=6-3 + 9 = 6.
The question asks for the sum of all values of kk that satisfy the tangency condition.

Anahtar Kavram

Determining the relationship between a line and a circle in a system of equations by setting the perpendicular distance from the center of the circle equal to its radius.

Alternatif Yöntem

Substitute y=kxy = k - x into the circle equation to obtain a quadratic equation in xx: (x4)2+(kx+1)2=18(x - 4)^2 + (k - x + 1)^2 = 18. Expanding and combining like terms yields 2x22(k+5)x+(k2+2k1)=02x^2 - 2(k + 5)x + (k^2 + 2k - 1) = 0. For the system to have exactly one real solution, the discriminant Δ\Delta of this quadratic equation must be zero: Δ=[2(k+5)]24(2)(k2+2k1)=0\Delta = [-2(k + 5)]^2 - 4(2)(k^2 + 2k - 1) = 0. Simplifying this equation leads to 4(k2+10k+25)8(k2+2k1)=0    k26k27=04(k^2 + 10k + 25) - 8(k^2 + 2k - 1) = 0 \implies k^2 - 6k - 27 = 0. By Vieta's formulas, the sum of the solutions to this quadratic equation for kk is given by ba=61=6-\frac{b}{a} = -\frac{-6}{1} = 6.
Tahmini Süre:2m 30s
Soru 36Soru

A system of equations consists of the quadratic function f(x)=x2+6x2f(x) = -x^2 + 6x - 2 and the linear function g(x)=2x+1g(x) = 2x + 1. If the graphs of ff and gg intersect at the points (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) in the xyxy-plane, what is the value of y1+y2y_1 + y_2?

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Cevap: 10

Cevap

10
By setting the two equations equal to each other, we obtain x2+6x2=2x+1-x^2 + 6x - 2 = 2x + 1. Rearranging terms to one side gives x24x+3=0x^2 - 4x + 3 = 0, which factors as (x1)(x3)=0(x-1)(x-3) = 0. The x-coordinates of the intersection points are x=1x = 1 and x=3x = 3. Substituting these into the linear equation gives the y-coordinates: for x=1x = 1, y=2(1)+1=3y = 2(1) + 1 = 3; for x=3x = 3, y=2(3)+1=7y = 2(3) + 1 = 7. Summing these y-coordinates gives 3+7=103 + 7 = 10.

Adım Adım Çözüm

1
Set the quadratic function equal to the linear function to find the x-coordinates of the intersection points.
x2+6x2=2x+1-x^2 + 6x - 2 = 2x + 1
At the points of intersection, the y-values of both functions must be equal.
2
Rearrange the equation into standard quadratic form and solve for xx by factoring.
x24x+3=0(x1)(x3)=0x=1 or x=3x^2 - 4x + 3 = 0 \Rightarrow (x - 1)(x - 3) = 0 \Rightarrow x = 1 \text{ or } x = 3
Factoring the quadratic equation gives the x-coordinates of the intersection points.
3
Substitute the x-coordinates back into the linear equation to find the corresponding y-coordinates.
For x1=1x_1 = 1, y1=2(1)+1=3y_1 = 2(1) + 1 = 3. For x2=3x_2 = 3, y2=2(3)+1=7y_2 = 2(3) + 1 = 7.
The linear equation g(x)=2x+1g(x) = 2x + 1 is simpler to use for finding the y-coordinates than the quadratic equation.
4
Sum the two y-coordinates.
y1+y2=3+7=10y_1 + y_2 = 3 + 7 = 10
The question asks for the sum of the y-coordinates of the intersection points.

Anahtar Kavram

Solving a system consisting of a linear equation and a quadratic equation by substitution or equating them.
Soru 37Soru
y=3x24x5y2x=4\begin{aligned} y &= 3x^2 - 4x - 5 \\ y - 2x &= 4 \end{aligned}

If (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) are the solutions to the system of equations above, and y1>y2y_1 > y_2, what is the value of x1+y2x_1 + y_2?

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Cevap: 5

Cevap

5
To find the solutions to the system of equations, substitute the expression for yy from the second equation into the first equation. First, rewrite the second equation as y=2x+4y = 2x + 4. Substituting this into the first equation yields 2x+4=3x24x52x + 4 = 3x^2 - 4x - 5. Rearranging terms to set the equation to zero gives 3x26x9=03x^2 - 6x - 9 = 0. Dividing the entire equation by 3 simplifies it to x22x3=0x^2 - 2x - 3 = 0. Factoring this quadratic equation gives (x3)(x+1)=0(x - 3)(x + 1) = 0, which yields the solutions x1=3x_1 = 3 and x2=1x_2 = -1. Next, find the corresponding yy-coordinates by substituting these xx-values back into the linear equation y=2x+4y = 2x + 4. For x=3x = 3, y1=2(3)+4=10y_1 = 2(3) + 4 = 10. For x=1x = -1, y2=2(1)+4=2y_2 = 2(-1) + 4 = 2. We are given that y1>y2y_1 > y_2, which confirms that (x1,y1)=(3,10)(x_1, y_1) = (3, 10) and (x2,y2)=(1,2)(x_2, y_2) = (-1, 2). Finally, calculate x1+y2x_1 + y_2, which is 3+2=53 + 2 = 5.

Adım Adım Çözüm

1
Rewrite the linear equation to express yy in terms of xx.
y=2x+4y = 2x + 4
This allows for substitution into the quadratic equation.
2
Substitute y=2x+4y = 2x + 4 into the quadratic equation and set to zero.
3x26x9=03x^2 - 6x - 9 = 0
To find the xx-coordinates of the intersection points.
3
Simplify and factor the quadratic equation.
(x3)(x+1)=0(x - 3)(x + 1) = 0, giving x=3x = 3 and x=1x = -1.
To solve for the xx-values of the intersection points.
4
Substitute the xx-values back into the linear equation to find the corresponding yy-values.
For x=3x = 3, y=10y = 10. For x=1x = -1, y=2y = 2. The intersection points are (3,10)(3, 10) and (1,2)(-1, 2).
To find the complete coordinates of the intersection points.
5
Identify (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) using the condition y1>y2y_1 > y_2, and compute x1+y2x_1 + y_2.
Since 10>210 > 2, y1=10y_1 = 10 (with x1=3x_1 = 3) and y2=2y_2 = 2 (with x2=1x_2 = -1). Then, x1+y2=3+2=5x_1 + y_2 = 3 + 2 = 5.
To compute the required target expression.

Anahtar Kavram

Solving a nonlinear system of equations by substituting a linear expression into a quadratic equation and solving the resulting quadratic equation.
Soru 38Soru
y=2x2kx+8y=4x10\begin{aligned} y &= 2x^2 - kx + 8 \\ y &= 4x - 10 \end{aligned}

In the system of equations above, kk is a constant. If the system has exactly one real solution, what is the product of all possible values of kk?

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Cevap: -128

Cevap

-128
To find the number of solutions to the system, set the two equations equal to each other: 2x2kx+8=4x102x^2 - kx + 8 = 4x - 10. Moving all terms to one side gives 2x2(k+4)x+18=02x^2 - (k + 4)x + 18 = 0. For this quadratic equation to have exactly one real solution, its discriminant, Δ=B24AC\Delta = B^2 - 4AC, must equal zero. Substituting the coefficients A=2A = 2, B=(k+4)B = -(k + 4), and C=18C = 18 into the discriminant formula gives ((k+4))24(2)(18)=0(-(k + 4))^2 - 4(2)(18) = 0, which simplifies to (k+4)2144=0(k + 4)^2 - 144 = 0. Solving this equation gives k+4=12    k=8k + 4 = 12 \implies k = 8, or k+4=12    k=16k + 4 = -12 \implies k = -16. The product of these possible values is 8×(16)=1288 \times (-16) = -128.

Adım Adım Çözüm

1
Equate the quadratic and linear equations to find the condition for intersection.
2x2kx+8=4x102x^2 - kx + 8 = 4x - 10
To find the points where the two graphs intersect, their yy-values must be set equal to each other.
2
Rearrange the terms to form a standard quadratic equation of the form Ax2+Bx+C=0Ax^2 + Bx + C = 0.
2x2(k+4)x+18=02x^2 - (k + 4)x + 18 = 0
Grouping terms allows us to determine the coefficients A=2A = 2, B=(k+4)B = -(k + 4), and C=18C = 18 to use in the discriminant.
3
Set the discriminant Δ=B24AC\Delta = B^2 - 4AC of the quadratic equation to 00.
[(k+4)]24(2)(18)=0    (k+4)2144=0[-(k + 4)]^2 - 4(2)(18) = 0 \implies (k + 4)^2 - 144 = 0
A system of a line and a parabola has exactly one real solution (meaning the line is tangent to the parabola) when the resulting quadratic equation has exactly one real root, which corresponds to a discriminant of zero.
4
Solve for the possible values of kk and calculate their product.
k+4=±12    k=8k + 4 = \pm 12 \implies k = 8 or k=16k = -16. The product is 8×(16)=1288 \times (-16) = -128.
Extracting the square root yields two possible values for kk, and multiplying them gives the requested product.

Anahtar Kavram

Using the discriminant of a quadratic equation to find parameter values that make a linear-quadratic system have exactly one real solution.

Alternatif Yöntem

Once the quadratic equation (k+4)2144=0(k + 4)^2 - 144 = 0 is simplified to k2+8k128=0k^2 + 8k - 128 = 0, Vieta's formulas can be applied directly to find the product of the possible values of kk. According to Vieta's formulas, the product of the roots of a quadratic equation ak2+bk+c=0ak^2 + bk + c = 0 is given by c/ac/a. Here, a=1a = 1 and c=128c = -128, so the product of the roots is 128/1=128-128 / 1 = -128.
Tahmini Süre:2m 0s
Soru 39Soru

Consider the system of equations below:

y=2x2+kx+9y=2x+1\begin{aligned} y &= 2x^2 + kx + 9 \\ y &= -2x + 1 \end{aligned}

In the system of equations above, kk is a positive constant. If the system has exactly one real solution, what is the value of kk?

Cevabı ve açıklamayı göster

Cevap: 6

Cevap

The value of the positive constant kk is 6.
By substituting the linear equation into the quadratic equation, we obtain the equation 2x2+(k+2)x+8=02x^2 + (k+2)x + 8 = 0. For the system to have exactly one real solution, the discriminant of this quadratic equation, Δ=b24ac\Delta = b^2 - 4ac, must be equal to zero. Substituting a=2a = 2, b=k+2b = k+2, and c=8c = 8 into the discriminant formula gives (k+2)24(2)(8)=0(k+2)^2 - 4(2)(8) = 0, which simplifies to (k+2)2=64(k+2)^2 = 64. Solving for kk gives k+2=8k+2 = 8 or k+2=8k+2 = -8, resulting in k=6k = 6 or k=10k = -10. Since kk is specified to be a positive constant, the value of kk must be 6.

Adım Adım Çözüm

1
Substitute the expression for yy from the linear equation into the quadratic equation.
2x2+kx+9=2x+12x^2 + kx + 9 = -2x + 1
Setting the two expressions for yy equal to each other allows us to solve for the xx-coordinates of the intersection points.
2
Rearrange the equation into the standard quadratic form ax2+bx+c=0ax^2 + bx + c = 0.
2x2+(k+2)x+8=02x^2 + (k+2)x + 8 = 0
Grouping the terms by power of xx lets us identify the coefficients a=2a = 2, b=k+2b = k+2, and c=8c = 8.
3
Set the discriminant of the quadratic equation to zero.
(k+2)24(2)(8)=0(k+2)^2 - 4(2)(8) = 0, which simplifies to (k+2)264=0(k+2)^2 - 64 = 0
A quadratic equation has exactly one real solution if and only if its discriminant, b24acb^2 - 4ac, is equal to zero.
4
Solve for the positive constant kk.
k=6k = 6
Solving (k+2)2=64(k+2)^2 = 64 yields k+2=8k+2 = 8 or k+2=8k+2 = -8, which means k=6k = 6 or k=10k = -10. Since kk must be a positive constant, we select 6.

Anahtar Kavram

Determining the number of solutions of a quadratic-linear system using the discriminant.

Alternatif Yöntem

Alternatively, the quadratic equation 2x2+(k+2)x+8=02x^2 + (k+2)x + 8 = 0 has exactly one real solution when it is a perfect square trinomial. Factoring out the leading coefficient gives 2(x2+k+22x+4)=02(x^2 + \frac{k+2}{2}x + 4) = 0. For the term inside the parentheses to be a perfect square trinomial of the form x2+2dx+d2x^2 + 2dx + d^2, we must have d2=4d^2 = 4, which means d=±2d = \pm 2. Thus, the middle coefficient k+22\frac{k+2}{2} must equal 2d=±42d = \pm 4. Since kk is positive, we set k+22=4\frac{k+2}{2} = 4, which solves to k=6k = 6.
Tahmini Süre:1m 30s
Soru 40Soru

In the xyxy-plane, a system of equations consists of the circle with equation (x7)2+(y4)2=1(x - 7)^2 + (y - 4)^2 = 1 and the line y=kxy = kx, where kk is a positive constant. If the system has exactly one real solution and k>0.5k > 0.5, what is the value of kk?

Cevabı ve açıklamayı göster

Cevap: 0.75

Cevap

The correct answer is 3/4 (or 0.75).
The correct answer is 3/43/4 (or 0.750.75). Substituting the line y=kxy = kx into the circle equation and setting the discriminant of the resulting quadratic equation to zero yields a quadratic in kk: 48k256k+15=048k^2 - 56k + 15 = 0. Solving this equation gives two positive tangent slopes: k=5/12k = 5/12 and k=3/4k = 3/4. Since the problem specifies that k>0.5k > 0.5, we choose k=3/4k = 3/4, which equals 0.750.75. Alternatively, using geometry, the distance from the center (7,4)(7,4) to the line kxy=0kx - y = 0 must equal the radius 11. This gives 7k4k2+1=1\frac{|7k-4|}{\sqrt{k^2+1}} = 1. Squaring both sides yields (7k4)2=k2+1(7k-4)^2 = k^2+1, which simplifies to 48k256k+15=048k^2 - 56k + 15 = 0, giving the same values of kk.

Adım Adım Çözüm

1
Substitute the linear equation y=kxy = kx into the circle's quadratic equation (x7)2+(y4)2=1(x - 7)^2 + (y - 4)^2 = 1.
(x7)2+(kx4)2=1(x - 7)^2 + (kx - 4)^2 = 1
To find the points of intersection between the line and the circle, substitute the expression for yy from the linear equation into the circle's equation.
2
Expand the terms and write the equation in the standard quadratic form Ax2+Bx+C=0Ax^2 + Bx + C = 0.
(1+k2)x2(14+8k)x+64=0(1 + k^2)x^2 - (14 + 8k)x + 64 = 0
Expanding (x7)2(x - 7)^2 yields x214x+49x^2 - 14x + 49 and expanding (kx4)2(kx - 4)^2 yields k2x28kx+16k^2x^2 - 8kx + 16. Grouping the terms by powers of xx and subtracting 11 from both sides gives the standard form.
3
Set the discriminant of the quadratic equation to 00 to satisfy the condition of exactly one real solution.
Δ=[(14+8k)]24(1+k2)(64)=0\Delta = [-(14 + 8k)]^2 - 4(1 + k^2)(64) = 0
A quadratic equation has exactly one real solution if and only if its discriminant, B24ACB^2 - 4AC, is equal to zero. Geometrically, this means the line is tangent to the circle.
4
Simplify the discriminant equation and solve for kk.
48k256k+15=048k^2 - 56k + 15 = 0, which factors as (12k5)(4k3)=0(12k - 5)(4k - 3) = 0. Thus, k=512k = \frac{5}{12} or k=34k = \frac{3}{4}.
Simplifying (14+8k)2256(1+k2)=0(14 + 8k)^2 - 256(1 + k^2) = 0 gives 196+224k+64k2256256k2=0196 + 224k + 64k^2 - 256 - 256k^2 = 0, which simplifies to 192k2+224k60=0-192k^2 + 224k - 60 = 0. Dividing the entire equation by 4-4 yields the quadratic equation in kk.
5
Select the value of kk that satisfies the given condition k>0.5k > 0.5.
k=34k = \frac{3}{4} (or 0.750.75)
Since 5120.417\frac{5}{12} \approx 0.417 is less than 0.50.5 and 34=0.75\frac{3}{4} = 0.75 is greater than 0.50.5, the correct value is 3/43/4.

Anahtar Kavram

Solving a nonlinear system of equations involving a circle and a line by setting the discriminant of the substituted quadratic equation to zero to find the slope of the tangent lines.
Tahmini Süre:2m 30s
ÖncekiSayfa 2 / 3Sonraki
Nonlinear Systems of Equations Alıştırma Soruları — SAT — Sayfa 2 | Examkin