#### Answer

$120t^9$

#### Work Step by Step

Using the properties of radicals, the given expression, $
\sqrt[]{120t^9}\sqrt[]{120t^9}
,$ simplifies to
\begin{array}{l}\require{cancel}
\sqrt[]{120t^9(120t^9)}
\\\\=
\sqrt[]{(120t^9)^2}
\\\\=
120t^9
\end{array}