#### Answer

$xy$

#### Work Step by Step

Using the properties of radicals, the given expression, $
\sqrt{x^2y}\sqrt{y}
,$ simplifies to
\begin{array}{l}\require{cancel}
\sqrt{x^2y(y)}
\\\\=
\sqrt{x^2y^2}
\\\\=
\sqrt{(xy)^2}
\\\\=
xy
.\end{array}
Note that all variables represent positive real numbers.