If $x + \sqrt {({x^2} + 1)} = a,$ then $x =$

If ${a^{1/x}} = {b^{1/y}} = {c^{1/z}}$ and ${b^2} = ac$ then $x + z = $

If $a = \sqrt {(21)} - \sqrt {(20)} $ and $b = \sqrt {(18)} - \sqrt {(17),}  $ then

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

$\sqrt {(3 + \sqrt 5 )} $ is equal to

The value of the fifth root of $10^{10^{10}}$ is