Which expression is equivalent to (x + 3)(x - 3)?
Ax² + 9
Bx² - 9
Cx² + 6x + 9
Dx² - 6x - 9
Answer & Solution
Correct answer: B. x² - 9
By the difference of squares: (x + 3)(x - 3) = x² - 9. This is a key identity for SAT — it eliminates the middle cross-terms.
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