Освободите от знака корня в знаменателе 7/2√21= 22/√13-√2=

Решите задачу:

$\frac{7}{2 \sqrt{21} } = \frac{7\sqrt{21} }{2 \sqrt{21}*\sqrt{21} } = \frac{7\sqrt{21} }{2*21}= \frac{7\sqrt{21} }{42} = \frac{\sqrt{21} }{6} \\ \\ \frac{22}{\sqrt{13}-\sqrt{2} } = \frac{22(\sqrt{13}+\sqrt{2})}{(\sqrt{13}-\sqrt{2})(\sqrt{13}+\sqrt{2})} = \frac{22(\sqrt{13}+\sqrt{2})}{13-2} = \\ = \frac{22(\sqrt{13}+\sqrt{2})}{11}=2(\sqrt{13}+\sqrt{2})=2 \sqrt{13}+2 \sqrt{2}$