Answer
$4a^{27}$
Work Step by Step
Extracting the factors that are perfect powers of the index, the given expression, $
\sqrt[3]{64a^{81}}
,$ is equivalent to
\begin{align*}\require{cancel}
&
\sqrt[3]{(4a^{27})^3}
\\\\&=
4a^{27}
.\end{align*}
Hence, the given expression simplifies to $
4a^{27}
$.
