Advanced Math practice question

Answer: B. x = 3 and x = −3

x² = 9 gives x = ±3, or factor as (x − 3)(x + 3) = 0. The most common trap is choice A, forgetting the negative root; choice C confuses the value of x² with the value of x.

Why the other answers are wrong

A. x = 3 only

You found the positive square root but stopped there — since (−3)² = 9 as well, −3 is also a solution.

C. x = 9 and x = −9

You added 9 to both sides but never took the square root, so you reported the value of x² instead of x.

D. x = 81 and x = −81

You squared 9 instead of taking its square root; the equation asks for numbers whose square is 9, not 9 squared.

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