Answer
$f(x)=2x^2\sqrt[3]{5}$
Work Step by Step
Extracting the perfect cube factor of the radicand, the given function, $
f(x)=\sqrt[3]{40x^6}
,$ simplifies to
\begin{array}{l}\require{cancel}
f(x)=\sqrt[3]{40x^6}
\\\\
f(x)=\sqrt[3]{8x^6\cdot5}
\\\\
f(x)=\sqrt[3]{(2x^2)^3\cdot5}
\\\\
f(x)=2x^2\sqrt[3]{5}
.\end{array}