Đáp án:
c) \(x \in \emptyset \)
Giải thích các bước giải:
\(\begin{array}{l}
C3:\\
a)DK:x \ge 0;x \ne 1\\
b)P = \left[ {\dfrac{{\sqrt x \left( {\sqrt x - 1} \right) - \sqrt x \left( {\sqrt x + 1} \right)}}{{\left( {\sqrt x - 1} \right)\left( {\sqrt x + 1} \right)}}} \right].\dfrac{{\sqrt x + 1}}{2}\\
= \dfrac{{x - \sqrt x - x - \sqrt x }}{{\left( {\sqrt x - 1} \right)\left( {\sqrt x + 1} \right)}}.\dfrac{{\sqrt x + 1}}{2}\\
= \dfrac{{ - 2\sqrt x }}{{\left( {\sqrt x - 1} \right)\left( {\sqrt x + 1} \right)}}.\dfrac{{\sqrt x + 1}}{2}\\
= - \dfrac{{\sqrt x }}{{\sqrt x - 1}}\\
c)P = - 2\\
\to - \dfrac{{\sqrt x }}{{\sqrt x - 1}} = - 2\\
\to \dfrac{{\sqrt x }}{{\sqrt x - 1}} = 2\\
\to \sqrt x = 2\sqrt x - 1\\
\to \sqrt x = 1\\
\to x = 1\left( l \right)\\
\to x \in \emptyset
\end{array}\)
