Answer
$a]$ $\frac{18}{z}\sqrt \frac{1}{z}$
$b]$ $\frac{4a^{2}}{b}\sqrt 2$
Work Step by Step
$a]$ $\sqrt \frac{18^{2}}{z^{3}}=$ $18\sqrt \frac{1}{z^{2}\times z}=$ $\frac{18}{z}\sqrt \frac{1}{z}$
$b]$ $\sqrt \frac{32a^{4}}{b^{2}}=$ $\frac{1}{b}\sqrt \frac{4^{2}\times 2 \times a^{4}}{1}=$ $\frac{4a^{2}}{b}\sqrt 2$
