Đáp án:
\(\dfrac{{x - 7}}{{\sqrt x }}\)
Giải thích các bước giải:
\(\begin{array}{l}
DK:x > 0;x \ne 4\\
B = \left( {\dfrac{{\sqrt x }}{{\sqrt x - 2}} - \dfrac{7}{{x - 2\sqrt x }}} \right):\left( {\dfrac{4}{{x - 4}} + \dfrac{1}{{2 + \sqrt x }}} \right)\\
= \left[ {\dfrac{{x - 7}}{{\sqrt x \left( {\sqrt x - 2} \right)}}} \right]:\left[ {\dfrac{{4 + \sqrt x - 2}}{{\left( {\sqrt x - 2} \right)\left( {\sqrt x + 2} \right)}}} \right]\\
= \dfrac{{x - 7}}{{\sqrt x \left( {\sqrt x - 2} \right)}}.\dfrac{{\left( {\sqrt x - 2} \right)\left( {\sqrt x + 2} \right)}}{{\sqrt x + 2}}\\
= \dfrac{{x - 7}}{{\sqrt x }}
\end{array}\)
