3. Освободитесь от знака корня в знаменателе: a) $$\frac{18}{\sqrt{6}}$$; б) $$\frac{3}{\sqrt{11} + \sqrt{2}}$$.

a) $$\frac{18}{\sqrt{6}} = \frac{18\sqrt{6}}{\sqrt{6}\sqrt{6}} = \frac{18\sqrt{6}}{6} = 3\sqrt{6}$$ б) $$\frac{3}{\sqrt{11} + \sqrt{2}} = \frac{3(\sqrt{11} - \sqrt{2})}{(\sqrt{11} + \sqrt{2})(\sqrt{11} - \sqrt{2})} = \frac{3(\sqrt{11} - \sqrt{2})}{11 - 2} = \frac{3(\sqrt{11} - \sqrt{2})}{9} = \frac{\sqrt{11} - \sqrt{2}}{3}$$ Ответ: a) $$\boxed{3\sqrt{6}}$$ б) $$\boxed{\frac{\sqrt{11} - \sqrt{2}}{3}}$$