a) given equation is,
[tex]\begin{gathered} \sqrt[8]{x^8y^4z^{4\:}} \\ =\sqrt[8]{x^8}\sqrt[8]{y^4z^4} \\ =x\sqrt[8]{y^4z^4} \end{gathered}[/tex]b) the given equation is
[tex]\begin{gathered} \sqrt[3]{\sqrt{64x^6}} \\ =\sqrt[3]{8x^3} \\ =2\sqrt[3]{x^3} \\ =2x \end{gathered}[/tex]