Answer
$-7\sqrt{2x}$
Work Step by Step
Using the properties of radicals, the given expression, $
\sqrt{8x}-3\sqrt{18x}
,$ simplifies to
\begin{array}{l}\require{cancel}
\sqrt{4\cdot2x}-3\sqrt{9\cdot2x}
\\\\=
\sqrt{(2)^2\cdot2x}-3\sqrt{(3)^2\cdot2x}
\\\\=
2\sqrt{2x}-3(3)\sqrt{2x}
\\\\=
2\sqrt{2x}-9\sqrt{2x}
\\\\=
-7\sqrt{2x}
.\end{array}
