Giải thích các bước giải:
\(\begin{array}{l}
B2:\\
a.DK:x > 0;x \ne 1\\
Q = \left( {\frac{x}{4} - \frac{1}{2} + \frac{1}{{4x}}} \right).\left( {\frac{{x - 2\sqrt x + 1 - x - 2\sqrt x - 1}}{{\left( {\sqrt x + 1} \right)\left( {\sqrt x - 1} \right)}}} \right)\\
= \frac{{{x^2} - 2x + 1}}{{4x}}.\left( {\frac{{ - 4\sqrt x }}{{x - 1}}} \right)\\
= \frac{{{{\left( {x - 1} \right)}^2}}}{{4x}}.\left( {\frac{{ - 4\sqrt x }}{{x - 1}}} \right)\\
= - \frac{{x - 1}}{{\sqrt x }}\\
b.Q < 0\\
\to - \frac{{x - 1}}{{\sqrt x }} < 0\\
\to \frac{{x - 1}}{{\sqrt x }} > 0\\
Do:\sqrt x > 0\forall x > 0\\
\to x - 1 > 0\\
\to x > 1\\
c.Q = - 2\\
\to - \frac{{x - 1}}{{\sqrt x }} = - 2\\
\to \frac{{x - 1}}{{\sqrt x }} = 2\\
\to x - 1 = 2\sqrt x \\
\to \left[ \begin{array}{l}
\sqrt x = 1 + \sqrt 2 \\
\sqrt x = 1 - \sqrt 2 \left( l \right)
\end{array} \right. \to x = 3 + 2\sqrt 2
\end{array}\)
