Advanced Math practice question

Answer: A. 3x² + 6x − 10

(2x − 1)(2x + 1) = 4x² − 1. (x − 3)² = x² − 6x + 9. Subtract: 4x² − 1 − x² + 6x − 9 = 3x² + 6x − 10.

Why the other answers are wrong

B. 3x² − 10

The −6x inside (x − 3)² was dropped; subtracting it gives +6x.

C. 3x² − 6x − 10

Subtracting −6x gives +6x. The sign of the middle term flips when the square is subtracted.

D. 5x² + 6x − 10

4x² − x² is 3x²; the x² was added instead of subtracted.

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