#### Answer

$abc\sqrt[5]{ab^3c^4}$

#### Work Step by Step

Extracting the factors that are perfect roots of the given index, the given expression, $
\sqrt[5]{a^6b^8c^9}
,$ simplifies to
\begin{array}{l}\require{cancel}
\sqrt[5]{a^5b^5c^5\cdot ab^3c^4}
\\\\=
\sqrt[5]{(abc)^5\cdot ab^3c^4}
\\\\=
abc\sqrt[5]{ab^3c^4}
\end{array}
* Note that it is assumed that no radicands were formed by raising negative numbers to even powers.