Gmat prep-Problem Solving

[clinton]

The area of a square garden is A square feet and the perimeter is P feet. If A = 2P + 9, what is the perimeter of the garden, in feet?

-28
-36
-40
-56
-64


I solved this problem by choosing numbers. Is there a faster way to solve this?

[Anurag@Gurome]

Solution:
Let the side of square be x.
So, area A is x^2.
Perimeter P is 4x.
Or x^2 = 8x+9.
Or x = 9.
So, perimeter P is 36.