Answer
$(x+6)(x^2-2)$
Work Step by Step
Regroup to obtain
$(x^3+6x^2)+(-2x-12)$.
Factor out $x^2$ in the first group and $-2$ in the second:
$x^2(x+6)+(-2)(x+6)
\\=x^2(x+6)-2(x+6)$.
Factor out $(x+6)$ to obtain
$(x+6)(x^2-2)$.