Question

Ребят, подайте идею как решать

Answer 1

$frac{2}{sqrt{7}-sqrt{5}}=frac{7-5}{sqrt{7}-sqrt{5}}=\\frac{(sqrt{7}-sqrt{5})(sqrt{7}+sqrt{5})}{sqrt{7}+sqrt{5}}=sqrt{7}+sqrt{5}$
---------------
$frac{5}{sqrt{7}+sqrt{2}}=frac{7-2}{sqrt{7}+sqrt{2}}=\\frac{(sqrt{7}-sqrt{2})(sqrt{7}+sqrt{2})}{sqrt{7}+sqrt{2}}=sqrt{7}-sqrt{2}$
----------------------
$frac{3}{sqrt{5}-sqrt{2}}=frac{5-2}{sqrt{5}-sqrt{2}}=frac{(sqrt{5}-sqrt{2})(sqrt{5}+sqrt{2})}{sqrt{5}-sqrt{2}}=sqrt{5}+sqrt{2}$
---------
$3+frac{2}{sqrt{7}-sqrt{5}}-frac{5}{sqrt{7}+sqrt{2}}-frac{3}{sqrt{5}-sqrt{2}}=\\3+(sqrt{7}+sqrt{5})-(sqrt{7}-sqrt{2})-(sqrt{5}+sqrt{2})=\\3+sqrt{7}+sqrt{5}-sqrt{7}+sqrt{2}-sqrt{5}-sqrt{2}=3$