Advanced Math practice question

Answer: A. 4x − 2

f(x + 2) = (x + 2)² − 3(x + 2) = x² + 4x + 4 − 3x − 6 = x² + x − 2. Subtracting f(x) = x² − 3x leaves 4x − 2.

Why the other answers are wrong

B. 4x + 4

4x + 4 is (x + 2)² − x², forgetting the −3x parts.

C. 2x − 2

2x − 2 halves the x term.

D. 4x − 6

4x − 6 uses −3(x + 2) = −3x − 6 but forgets the +4 from the square.

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