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Zorluk: OrtaSystems of Linear Equations
Consider the system of linear equations in two variables xx and yy shown below:
3x+2y=16x4y=4\begin{aligned} 3x + 2y &= 16 \\ x - 4y &= -4 \end{aligned}
If (x,y)(x, y) is the unique solution to the system, what is the value of yx\frac{y}{x}?
  1. 12\frac{1}{2}Cevap
  2. B
    22
  3. C
    44
  4. D
    25\frac{2}{5}
  5. E
    66

Cevap

The value of yx\frac{y}{x} is 12\frac{1}{2}.
Solving the system by substitution gives x=4x = 4 and y=2y = 2. Dividing yy by xx gives 24=12\frac{2}{4} = \frac{1}{2}, which is the target ratio.

Adım Adım Çözüm

1
Isolate xx in the second equation.
x=4y4x = 4y - 4
Expressing xx in terms of yy allows for substitution into the first equation.
2
Substitute x=4y4x = 4y - 4 into the first equation.
3(4y4)+2y=16    12y12+2y=16    14y=28    y=23(4y - 4) + 2y = 16 \implies 12y - 12 + 2y = 16 \implies 14y = 28 \implies y = 2
Solving the single-variable equation determines the value of yy.
3
Substitute y=2y = 2 back into the isolated expression for xx.
x=4(2)4=4x = 4(2) - 4 = 4
Determines the corresponding value of xx.
4
Compute the required ratio yx\frac{y}{x}.
yx=24=12\frac{y}{x} = \frac{2}{4} = \frac{1}{2}
Evaluates the final expression requested by the prompt.

Anahtar Kavram

Solving systems of linear equations using substitution or elimination to evaluate a combined expression.
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