Question

Which of the following when added to 4a^2+9 will result in a perfect square for all integer values of a?

(A) 0
(B) 3a
(C) 6a
(D) 9a
(E) 12a

Answer 1

E. 12a

Explanation:

TBH no idea why thats correct.

Answer 2

(D) 9a

Explanation:

Given

4a^2 + 9

Add 9a to the expression

4a^2 + 9 + 9a

This can be written as

(2a)^2 + (3)^2 + (3)^2 a