Advanced Math practice question

Answer: C. x² + 10x + 25

(x + 5)² = (x + 5)(x + 5) = x² + 5x + 5x + 25 = x² + 10x + 25. The classic trap is choice A, distributing the square over the sum and dropping the middle term 2·5·x = 10x.

Why the other answers are wrong

A. x² + 25

You squared each term separately, but (x + 5)² means (x + 5)(x + 5), which produces a middle term of 2·5·x = 10x.

B. x² + 5x + 25

You picked up only one of the two 5x terms from the multiplication — the FOIL outer and inner products are both 5x, totaling 10x.

D. x² + 10x + 5

You got the middle term right but wrote the last term as 5 instead of 5·5 = 25.

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