[tex]\bf \sqrt{\cfrac{8}{x^6}}\qquad
\begin{cases}
8=2\cdot 2\cdot 2\\
\qquad 2^2\cdot 2\\
x^6=x^{3\cdot 2}\\
\qquad (x^3)^2
\end{cases}\implies \sqrt{\cfrac{2^2\cdot 2}{(x^3)^2}}\implies \cfrac{\sqrt{2^2\cdot 2}}{\sqrt{(x^3)^2}}\implies \cfrac{2\sqrt{2}}{x^3}[/tex]
