Answer
$\color{blue}{14m^2n}$
Work Step by Step
Factor the radicand so that at least one factor is a perfect square:
$=\sqrt{(14m^2n)^2}$
RECALL:
For non-negative real numbers $a$, $\sqrt{a^2}=a$
Using the rule above gives:
$\sqrt{(14m^2n)^2}=\color{blue}{14m^2n}$
