Answer
$10x\sqrt{2x}$
Work Step by Step
Using the properties of radicals, then,
\begin{array}{l}
2\sqrt{2x^3}+4x\sqrt{8x}
\\=
2\sqrt{x^2\cdot2x}+4x\sqrt{4\cdot2x}
\\=
2\cdot x\sqrt{2x}+4x\cdot2\sqrt{2x}
\\=
2x\sqrt{2x}+8x\sqrt{2x}
\\=
10x\sqrt{2x}
.\end{array}