Question

Освободиться от иррациональности в знаменателе

-39/√12+√5

Answer 1

$\frac{-39}{\sqrt{12} +\sqrt{5} }=-\frac{39*(\sqrt{12}-\sqrt{5})}{(\sqrt{12}+\sqrt{5})(\sqrt{12}-\sqrt{5})}=-\frac{39*(\sqrt{12}-\sqrt{5})}{(\sqrt{12})^{2}-(\sqrt{5})^{2}}=-\frac{39*(\sqrt{12}-\sqrt{5})}{12-5}=-\frac{39*(\sqrt{12}-\sqrt{5})}{7}$