a,$\sqrt[]{\frac{1}{500}}$ =$\frac{1}{10\sqrt[]{5} }$ = $\frac{\sqrt[]{5}}{50}$
b,$\sqrt[]{\frac{4}{540}}$ = $\frac{2}{6\sqrt[]{15}}$ =$\frac{2\sqrt[]{15}}{90}$
c,$\sqrt[]{\frac{3}{50}}$ = $\frac{\sqrt[]{3}}{5\sqrt[]{2}}$ = $\frac{\sqrt[]{6}}{10}$
d,ab$\sqrt[]{\frac{a}{b}}$ = $\sqrt[]{(a.b)^{2} .\frac{a}{b}}$ =$\sqrt[]{a^{3}.b}$ = a$\sqrt[]{ab}$