14. $$ \sqrt{\frac{36x^2}{y^4}} $$ при $$ x = 6 $$ и $$ y = 2 $$.
$$ \sqrt{\frac{36x^2}{y^4}} = \frac{\sqrt{36x^2}}{\sqrt{y^4}} = \frac{\sqrt{36} \cdot \sqrt{x^2}}{\sqrt{y^4}} = \frac{6 \cdot |x|}{y^2} = \frac{6 \cdot |6|}{2^2} = \frac{6 \cdot 6}{4} = \frac{36}{4} = 9 $$
Ответ: 9