Question

If y = (x + 3)2, then (-2x - 6)2 must equal which of the following?

Answer 1

$(-2x-6)^2=(-2(x+3))^2=(-2)^2 \times (x+3)^2=4(x+3)^2 \\ \\ y=(x+3)^2 \hbox{ so } 4(x+3)^2=4y$

The answer is D.