#### Answer

$2xy\sqrt{2}$

#### Work Step by Step

The variables are assumed to be non-zero since they are also in the denominator.
RECALL:
$\dfrac{\sqrt{a}}{\sqrt{b}} = \sqrt{\frac{a}{b}}$ where $a$ and $b$ are non-negative and $b\ne0.$
Use the rule above to have
$\require{cancel}
\sqrt{\dfrac{56x^5y^5}{7xy}}
\\=\sqrt{\dfrac{\cancel{56}8\cancel{x^5}x^4\cancel{y^5}y^4}{\cancel{7xy}}}
\\=\sqrt{8x^4y^4}
\\=\sqrt{4x^4y^4(2)}
\\=\sqrt{(2x^2y^2)^2(2)}
\\=2xy\sqrt{2}.$