Answer
$3x^2(3x + 4)(5x+4)$
Work Step by Step
We factor out $x^2(3x + 4)$ and distribute, combine like terms, and simplify as follows:
\begin{align*}
3x^2(3x + 4)^2& + x^3 \cdot 2(3x + 4) \cdot 3\\
&=x^2(3x + 4)[3(3x+4)+6x]\\
&=x^2(3x + 4)[9x+12+6x]\\
&=x^2(3x + 4)(15x+12)\\
&=3x^2(3x + 4)(5x+4).
\end{align*}
