Advanced Math practice question

Answer: A. 2ab

(a + b)² = a² + 2ab + b². Subtracting a² + b² leaves 2ab.

Why the other answers are wrong

B. ab

The cross term in (a + b)² is 2ab, not ab.

C. 0

(a + b)² is not the same as a² + b²; the difference is the cross term 2ab.

D. 2a² + 2b²

2a² + 2b² adds the squares instead of cancelling them.

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