Advanced MathMediumValue of a perfect-square trinomial with a linear term
Advanced Math practice question
If x + y = 4, what is the value of x² + 2xy + y² − 3(x + y)?
Answer: 4
x² + 2xy + y² = (x + y)² = 16, and 3(x + y) = 12. So the value is 16 − 12 = 4.
Common wrong answers
- If you answered 1
- 1 comes from 4 − 3, forgetting to square the sum.
- If you answered 13
- 13 comes from 16 − 3, not multiplying the 3 by (x + y).
- If you answered 28
- 28 adds 12 instead of subtracting.
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