Question

Difficulty: MediumSimplifying Expressions and Combining Like Terms

When the expression 4x(x−2y)−(2x−3y)2+5y(2x−y)4x(x - 2y) - (2x - 3y)^2 + 5y(2x - y) is simplified to the form Ax2+Bxy+Cy2Ax^2 + Bxy + Cy^2, where AA, BB, and CC are constants, what is the value of BB?

Answer: 14

Answer

The value of the coefficient BB is 14.
Expanding the entire expression yields 4x2−8xy−4x2+12xy−9y2+10xy−5y24x^2 - 8xy - 4x^2 + 12xy - 9y^2 + 10xy - 5y^2. Grouping and combining the xyxy terms gives (−8+12+10)xy=14xy(-8 + 12 + 10)xy = 14xy. Therefore, the coefficient BB is 14.

Step-by-Step Solution

1
Expand the first term
4x2−8xy4x^2 - 8xy
Distribute 4x4x to both terms inside the parentheses: 4x(x)−4x(2y)=4x2−8xy4x(x) - 4x(2y) = 4x^2 - 8xy.
2
Expand the squared binomial and apply the negative sign
−4x2+12xy−9y2-4x^2 + 12xy - 9y^2
Use the binomial expansion formula (2x−3y)2=4x2−12xy+9y2(2x - 3y)^2 = 4x^2 - 12xy + 9y^2, then multiply each term by −1-1.
3
Expand the third term
10xy−5y210xy - 5y^2
Distribute 5y5y to both terms inside the parentheses: 5y(2x)−5y(y)=10xy−5y25y(2x) - 5y(y) = 10xy - 5y^2.
4
Combine the coefficients of the like terms
0x2+14xy−14y20x^2 + 14xy - 14y^2
Sum the coefficients for each corresponding variable group: (4−4)x2+(−8+12+10)xy+(−9−5)y2(4 - 4)x^2 + (-8 + 12 + 10)xy + (-9 - 5)y^2.

Key Concept

Simplifying Algebraic Expressions and Combining Like Terms
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