Đáp án:
$\begin{array}{l}
E = \dfrac{{5\sqrt 2 - 2\sqrt 5 }}{{\sqrt 5 - \sqrt 2 }} + \dfrac{6}{{2 - \sqrt {10} }} - \dfrac{{20}}{{\sqrt {10} }}\\
= \dfrac{{\sqrt 5 .\sqrt 2 .\left( {\sqrt 5 - \sqrt 2 } \right)}}{{\sqrt 5 - \sqrt 2 }} + \dfrac{{6\left( {2 + \sqrt {10} } \right)}}{{4 - 10}} - 2\sqrt {10} \\
= \sqrt {10} - 2 - \sqrt {10} - 2\sqrt {10} \\
= - 2 - 2\sqrt {10}
\end{array}$
