Đáp án:
$\begin{array}{l}
Dkxd:x \ge 0;x \ne 4\\
A = \left( {\dfrac{1}{{\sqrt x + 2}} + \dfrac{1}{{\sqrt x - 2}}} \right).\left( {1 + 2\sqrt x } \right)\\
= \dfrac{{\sqrt x - 2 + \sqrt x + 2}}{{\left( {\sqrt x + 2} \right)\left( {\sqrt x - 2} \right)}}.\left( {2\sqrt x + 1} \right)\\
= \dfrac{{2\sqrt x }}{{x - 4}}.\left( {2\sqrt x + 1} \right)\\
= \dfrac{{4x + 2\sqrt x }}{{x - 4}}
\end{array}$