Giải thích các bước giải:
\[\begin{array}{l}
P = \left( {\frac{{4\sqrt x }}{{2 + \sqrt x }} + \frac{{8x}}{{4 - x}}} \right):\left( {\frac{{\sqrt x - 1}}{{x - 2\sqrt x }} - \frac{2}{{\sqrt x }}} \right)\left( {\left\{ \begin{array}{l}
x > 0\\
x \ne 4
\end{array} \right.} \right)\\
\Leftrightarrow P = \left( {\frac{{4\sqrt x \left( {2 - \sqrt x } \right)}}{{\left( {2 + \sqrt x } \right)\left( {2 - \sqrt x } \right)}} + \frac{{8x}}{{\left( {2 - \sqrt x } \right)\left( {2 + \sqrt x } \right)}}} \right):\left( {\frac{{\sqrt x - 1}}{{\sqrt x \left( {\sqrt x - 2} \right)}} - \frac{{2\left( {\sqrt x - 2} \right)}}{{\sqrt x \left( {\sqrt x - 2} \right)}}} \right)\\
\Leftrightarrow P = \left( {\frac{{8\sqrt x - 4x + 8x}}{{\left( {2 + \sqrt x } \right)\left( {2 - \sqrt x } \right)}}} \right):\left( {\frac{{\sqrt x - 1 - 2\sqrt x + 4}}{{\sqrt x \left( {\sqrt x - 2} \right)}}} \right)\\
\Leftrightarrow P = \left( {\frac{{4\sqrt x \left( {2 + \sqrt x } \right)}}{{\left( {2 + \sqrt x } \right)\left( {2 - \sqrt x } \right)}}} \right):\left( {\frac{{3 - \sqrt x }}{{\sqrt x \left( {\sqrt x - 2} \right)}}} \right) = \frac{{4\sqrt x }}{{2 - \sqrt x }}.\frac{{\sqrt x \left( {\sqrt x - 2} \right)}}{{3 - \sqrt x }} = \frac{{4x}}{{\sqrt x - 3}}
\end{array}\]
b, Thay x=25 vào P ta được P=50
