Answer
$(x-3)(x^2+4)$
Work Step by Step
Regroup the terms to obtain:
$=(x^3-3x^2)+(4x-12)$
Factor out the greatest common factor of each group to obtain:
$=x^2(x-3) + 4(x-3)$
The $GCF$ for the two terms is a binomial, $(x-3)$. Even though it is a binomial, we can factor it out just like we would factor out a number or a variable. Thus, we factor out the binomial to obtain:
$=(x-3)(x^2+4)$