Answer
$7x\sqrt{x}$.
Work Step by Step
The given expression is
$=\sqrt{49x^3}$
Factor as square terms.
$=\sqrt{49x^2\cdot x}$
Use product property of square roots.
$=\sqrt{49x^2}\cdot \sqrt{x}$
Use $49=7^2$.
$=\sqrt{7^2x^2}\cdot \sqrt{x}$
Simplify.
$=7x\sqrt{x}$.
