Answer
$3(x-6)(x+2)$
Work Step by Step
Factor out $3$ to obtain:
$=3(x^2-4x-12)$
RECALL:
A trinomial of the form $x^2+bx+c$ can be factored if there are integers $d$ and $e$ such that $c=de$ and $b=d+e$.
The trinomial's factored form will be:
$x^2+bx+c=(x+d)(x+e)$
The trinomial above has $b=-4$ and $c=-12$.
Note that $-12=-6(2)$ and $-4= (-6)+2$.
This means that $d=-6$ and $e=2$
Thus, the factored form of the trinomial is:
$(x-6)(x+2)$
Therefore, the completely factored form of the given expression is:
$3(x-6)(x+2)$