The value of ${{15} \over {\sqrt {10} + \sqrt {20} + \sqrt {40} - \sqrt 5 - \sqrt {80} }}$ is
$\sqrt 5 (5 + \sqrt 2 )$
$\sqrt 5 (2 + \sqrt 2 )$
$\sqrt 5 (1 + \sqrt 2 )$
$\sqrt 5 (3 + \sqrt 2 )$
If $x = {2^{1/3}} - {2^{ - 1/3}},$ then $2{x^3} + 6x = $
The equation $\sqrt {(x + 1)} - \sqrt {(x - 1)} = \sqrt {(4x - 1)} $, $x \in R$ has
$\sqrt {(3 + \sqrt 5 )} $ is equal to
${{\sqrt {(5/2)} + \sqrt {(7 - 3\sqrt 5 )} } \over {\sqrt {(7/2)} + \sqrt {(16 - 5\sqrt 7 )} }}=$
${{{{[4 + \sqrt {(15)} ]}^{3/2}} + {{[4 - \sqrt {(15)} ]}^{3/2}}} \over {{{[6 + \sqrt {(35)} ]}^{3/2}} - {{[6 - \sqrt {(35)} ]}^{3/2}}}} = $