Answer
$3x$
Work Step by Step
RECALL:
(i) For any non-negative real numbers $a$ and $b$,
$\sqrt{\dfrac{a}{b}} = \dfrac{\sqrt{a}}{\sqrt{b}}$ and $\dfrac{\sqrt{a}}{\sqrt{b}} = \sqrt{\dfrac{a}{b}}$.
(ii) For any non-negative real number $a$, $\sqrt{a^2}=a$.
Use rule (i) above to obtain
$\require{cancel}
\sqrt{\dfrac{72x^3}{8x}}
\\=\sqrt{\dfrac{\cancel{72}9\cancel{x^3}x^2}{\cancel{8}\cancel{x}}}
\\=\sqrt{9x^2}
\\=\sqrt{(3x)^2}.$
Use rule (ii) above to obtain
$3x.$
