Giải thích các bước giải:
Ta có:
\(\begin{array}{l}
P = \dfrac{{\sqrt x - 3}}{{ - x + \sqrt x - 1}}.\dfrac{{\sqrt x + 1}}{{\sqrt x - 3}}\\
= \dfrac{{\sqrt x + 1}}{{ - x + \sqrt x - 1}}\\
= - \dfrac{{\sqrt x + 1}}{{x - \sqrt x + 1}}\\
= - \dfrac{{\sqrt x + 1}}{{\left( {x - \sqrt x + \dfrac{1}{4}} \right) + \dfrac{3}{4}}}\\
= - \dfrac{{\sqrt x + 1}}{{{{\left( {\sqrt x - \dfrac{1}{2}} \right)}^2} + \dfrac{3}{4}}}\\
\dfrac{{\sqrt x + 1}}{{{{\left( {\sqrt x - \dfrac{1}{2}} \right)}^2} + \dfrac{3}{4}}} > 0,\,\,\,\forall x \ge 0,x \ne 4,x \ne 9\\
\Rightarrow P = - \dfrac{{\sqrt x + 1}}{{{{\left( {\sqrt x - \dfrac{1}{2}} \right)}^2} + \dfrac{3}{4}}} < 0,\,\,\,\forall x \ge 0,x \ne 4,x \ne 9\\
\left| P \right| > 0,\,\,\,\forall x \ge 0,x \ne 4,x \ne 9\\
\Rightarrow \left| P \right| > P
\end{array}\)
