Question

Racionalizar M
$m = \frac{1}{ \sqrt{5} + \sqrt{3} } + \frac{1}{ \sqrt{7} + \sqrt{5} } - \frac{2}{ \sqrt{7} + \sqrt{3} }$
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Answer 1

$m = \frac{2\sqrt{5}-\sqrt{3}-\sqrt{7}}{4}$          ??