Write $\sqrt{\dfrac{a}{5b}}$ without denominator under the radical sign
Solution 1:
You have$$\sqrt\frac{a}{5b}=\sqrt\frac{5ab}{5^2b^2}=\frac{\sqrt{5ab}}{5|b|}.$$
Solution 2:
$$\sqrt{\frac{a}{5b}}=\sqrt{\frac{a}{5b}\frac{5b}{5b}}=\frac{\sqrt{5ab}}{\sqrt{5^2b^2}}=\frac{1}{5|b|}\sqrt{5ab}$$