Answer:
C
Step-by-step explanation:
Comment
This is called the difference of squares. Both sides of the minus sigh must be perfect squares or able to be factored in such a way that you are left with perfect squares. 36x^2 is a perfect square. If you take its square root, you get √36x^2 or 6x. That makes B and D incorrect. So what about A and C?
A:The left side of 36x^2 is correct, but the right side is not. The left side of 36x^2 has a square root of 6x.
The right side has been left alone and it shouldn't be.
The 9 is a perfect square. Its square root is 3. That makes C the answer.
