Chapter 10 - Section 10.5 - Rationalizing Numerators and Denominators of Radical Expressions - Exercise Set - Page 717: 16

$\dfrac{-5\sqrt{2}}{\sqrt{11}}=\dfrac{-5\sqrt{22}}{11}$

$\dfrac{-5\sqrt{2}}{\sqrt{11}}$ Multiply the fraction by $\dfrac{\sqrt{11}}{\sqrt{11}}$ and simplify: $\dfrac{-5\sqrt{2}}{\sqrt{11}}=\dfrac{-5\sqrt{2}}{\sqrt{11}}\cdot\dfrac{\sqrt{11}}{\sqrt{11}}=\dfrac{-5\sqrt{22}}{\sqrt{11^{2}}}=\dfrac{-5\sqrt{22}}{11}$