Answer
The solutions are $3$ and $-9$.
Work Step by Step
$ x^{2}+6x+9=36\qquad$ ...write left side as a binomial squared.
$(x+3)^{2}=36\qquad$ ...take square roots of each side.
$ x+3=\pm 6\qquad$ ...add $-3$ to each side.
$ x+3-3=\pm 6-3\qquad$ ...simplify.
$ x=-3\pm 6\qquad$ ...write as separate equations.
$x=-3+6$ or $ x=-3-6\qquad$ ...simplify.
$x=3$ or $x=-9$
