Answer
$16x^{6}$
Work Step by Step
Using $(x^ay^b)^c=x^{ac}y^{bc}$ or the products-to-powers rule, the given expression, $
(4x^3)^2
,$ simplifies to
\begin{array}{l}\require{cancel}
4^{1(2)}x^{3(2)}
\\\\=
4^{2}x^{6}
\\\\=
16x^{6}
.\end{array}