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