Giải thích các bước giải:
\(\begin{array}{l}
B = \left[ {\frac{{3\sqrt x + 6 + \sqrt x \left( {\sqrt x + 2} \right)}}{{\left( {\sqrt x + 2} \right)\left( {\sqrt x - 2} \right)}}} \right].\frac{{\sqrt x - 3}}{{\left( {\sqrt x - 3} \right)\left( {\sqrt x + 3} \right)}}\\
= \frac{{3\sqrt x + 6 + x + 2\sqrt x }}{{\left( {\sqrt x + 2} \right)\left( {\sqrt x - 2} \right)}}.\frac{1}{{\left( {\sqrt x + 3} \right)}}\\
= \frac{{\left( {\sqrt x + 2} \right)\left( {\sqrt x + 3} \right)}}{{\left( {\sqrt x + 2} \right)\left( {\sqrt x - 2} \right)\left( {\sqrt x + 3} \right)}}\\
= \frac{1}{{\sqrt x - 2}}
\end{array}\)
