Answer
$$(x-6)(x+6)$$
Work Step by Step
Since the coefficient of the squared term is one, we know that the expression must factor to:
$$ (x\pm a)(x\pm b)$$
Here, we see that a and b must multiply to get $-36$ and add to get $0$. Thus, we find that the solution is:
$$(x-6)(x+6)$$