Answer
$3y^9\sqrt{10y}$
Work Step by Step
Getting the perfect factors and then extracting its root, the simplified form of the given expression, $
\sqrt{90y^{19}}
,$ is
\begin{array}{l}\require{cancel}
\sqrt{9y^{18}\cdot 10y}
\\\\=
\sqrt{(3y^9)^2\cdot 10y}
\\\\=
3y^9\sqrt{10y}
.\end{array}
Note that variables are assumed to represent positive real numbers.
