Question

звільнини від радикала знаменник дробу!!

Answer 1

$\frac{13}{2\sqrt{5}-\sqrt{7}}=\frac{13(2\sqrt{5}+\sqrt{7})}{(2\sqrt{5}-\sqrt{7})(2\sqrt{5}+\sqrt{7})} =\frac{13(2\sqrt{5}+\sqrt{7})}{(2\sqrt{5})^2-(\sqrt{7})^2}=\frac{13(2\sqrt{5}+\sqrt{7})}{20-7}=\frac{13(2\sqrt{5}+\sqrt{7})}{13}=2\sqrt{5}+\sqrt{7}$