Answer
$(x+2)(x+4)$
Work Step by Step
Regroup the terms to obtain:
$=(x^2+2x)+(4x+8)$
Factor out the greatest common factor of each group to obtain:
$=x(x+2) + 4(x+2)$
The $GCF$ for the two terms is a binomial, $(x+2)$. 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:
$=(x+2)(x+4)$