Question

simply by rationaliaing the denominator​

Answer 1

√7-√5/√7+√5

.√7-√5×√7-√5/√7+√5×√7-√5

7+√35-√35+5/7-5

12/2

6

Answer 2

Here is your solution :-

$\frac{ \sqrt{7} - \sqrt{5} }{ \sqrt{7} + \sqrt{5} } \\ \\ = \frac{ \sqrt{7} - \sqrt{5} }{ \sqrt{7} + \sqrt{5} } \: \times \frac{ \sqrt{7} - \sqrt{5} }{ \sqrt{7} - \sqrt{5} } \\ \\ = \frac{ {( \sqrt{7 } - \sqrt{5}) }^{2} }{ { \sqrt{7} }^{2} - { \sqrt{5} }^{2} } \\ \\ = \frac{ { \sqrt{7} }^{2} + { \sqrt{5} }^{2} - 2( \sqrt{7})( \sqrt{5})}{7 - 5} \\ \\ = \frac{7 + 5 - 2 \sqrt{35} }{2} \\ \\ = \frac{12 -2 \sqrt{35} }{2} \\ \\ = 6 - \sqrt{35}$

Hope it helps :)