Chapter 10 - Exponents and Radicals - 10.4 Dividing Radical Expressions - 10.4 Exercise Set - Page 654: 70

$\dfrac{7a}{\sqrt{42ab}}$

Rationalizing the numerator, the given expression, $ \sqrt{\dfrac{7a}{6b}} ,$ is equivalent to \begin{array}{l} \sqrt{\dfrac{7a}{6b}\cdot\dfrac{7a}{7a}} \\\\= \sqrt{\dfrac{(7a)^2}{42ab}} \\\\= \dfrac{7a}{\sqrt{42ab}} .\end{array}