#### Answer

$4|x|\sqrt{3x}$

#### Work Step by Step

Factor the radicand (expression inside the radical sign) so that at least one factor is a square to obtain:
$=\sqrt{16x^2(3x)}
\\=\sqrt{4^2x^2(3x)}$
The principal square root is always non-negative.
Thus, to make sure that the principal square root of $x^2$ is non-negative, use absolute value bars to obtain:
$=4|x|\sqrt{3x}$