Đáp án:
$\begin{array}{l}
A = \frac{{\sqrt x + 1}}{{\sqrt x - 1}} + \frac{{\sqrt x - 1}}{{\sqrt x + 1}} + \frac{{3\sqrt x + 1}}{{1 - x}}\\
= \frac{{\left( {\sqrt x + 1} \right)\left( {\sqrt x + 1} \right) + \left( {\sqrt x - 1} \right).\left( {\sqrt x - 1} \right) - 3\sqrt x - 1}}{{\left( {\sqrt x + 1} \right)\left( {\sqrt x - 1} \right)}}\\
= \frac{{x + 2\sqrt x + 1 + x - 2\sqrt x + 2 - 3\sqrt x - 1}}{{\left( {\sqrt x + 1} \right)\left( {\sqrt x - 1} \right)}}\\
= \frac{{2x - 3\sqrt x + 2}}{{\left( {\sqrt x + 1} \right)\left( {\sqrt x - 1} \right)}}\\
= \frac{{2x - 3\sqrt x + 2}}{{x - 1}}
\end{array}$
