Answer
{$-3-\sqrt {7},-3+\sqrt {7}$}
Work Step by Step
Given: $x^2+6x=-2$
We need to add $3^2$ to complete the square.
Thus,
$x^2+6x+3^2=-2+9$
or, $x^2+(2)(1)(3x)+3^2=7$
or, $(x+3)^2=7$
or, $(x+3)=\pm \sqrt {7}$
or, $x=-3- \sqrt {7},-3+\sqrt {7}$
Hence, solution set is $x=${$-3-\sqrt {7},-3+\sqrt {7}$}