Answer
$a^2(2b+3a)(4b^2-6ab+9a^2)$
Work Step by Step
Factoring the $GCF=
a
$ results to $
a(8b^3+27a^3)
$. Using $a^3+b^3=(a+b)(a^2-ab+b^2)$, or the factoring of the sum/difference of two cubes, then,
\begin{array}{l}
a(8b^3+27a^3)
\\=
a^2[(2b)+(3a)][(2b)^2-(2b)(3a)+(3a)^2)
\\=
a^2(2b+3a)(4b^2-6ab+9a^2)
.\end{array}
