Advanced Math practice question

Answer: A. 9x² − 4

The two factors differ only in the middle sign, so the middle terms cancel: 9x² − 6x + 6x − 4 = 9x² − 4. This is the difference-of-squares pattern in reverse.

Why the other answers are wrong

B. 9x² + 4

The constant is 2 × (−2) = −4, not +4.

C. 9x² − 12x − 4

The middle terms −6x and +6x cancel each other; there's no −12x.

D. 3x² − 4

(3x)² is 9x², not 3x². The coefficient is squared too.

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