Answer
{$-6,2$}
Work Step by Step
We will factor this trinomial by breaking up the middle term of the trinomial. This is in accordance with the rules of factoring trinomials.
$x^{2}+4x-12=0$
$x^{2}-2x+6x-12=0$
$x(x-2)+6(x-2)=0$
$(x-2)(x+6)=0$
$(x-2)=0$ and $(x+6)=0$
$x=2$ and $x=-6$
Therefore, the solution set is {$-6,2$}.