Chapter 7 - Section 7.5 - Rationalizing Denominators and Numerators of Radical Expressions - Exercise Set - Page 445: 9

$\dfrac{3\sqrt{2x}}{4x}$

The rationalized form of $ \dfrac{3}{\sqrt{8x}} $ is \begin{array}{l} \dfrac{3}{\sqrt{8x}}\cdot\dfrac{\sqrt{2x}}{\sqrt{2x}} \\\\= \dfrac{3\sqrt{2x}}{\sqrt{16x^2}} \\\\= \dfrac{3\sqrt{2x}}{4x} .\end{array}