# Come solve this if u think you are smart=)

$\frac{1}{{\sqrt k + \sqrt {k + 1} }} = \left( {\frac{1}{{\sqrt k + \sqrt {k + 1} }}} \right)\frac{{\sqrt k - \sqrt {k + 1} }}{{\sqrt k - \sqrt {k + 1} }} = \sqrt {k + 1} - \sqrt k$