Giải thích các bước giải:
\(\begin{array}{l}
a.DK:x \ge 0;x \ne 1\\
B = \frac{{\sqrt x + 1 - \sqrt x + 1 - 2\sqrt x }}{{2\left( {\sqrt x - 1} \right)\left( {\sqrt x + 1} \right)}}\\
= \frac{{2\left( {1 - \sqrt x } \right)}}{{2\left( {\sqrt x - 1} \right)\left( {\sqrt x + 1} \right)}} = \frac{{ - 1}}{{\sqrt x + 1}}\\
b.x = 3\\
\to B = \frac{{ - 1}}{{\sqrt 3 + 1}} = \frac{{1 - \sqrt 3 }}{2}\\
c.\left| B \right| = \frac{1}{2}\\
\to \left[ \begin{array}{l}
B = \frac{1}{2}\\
B = - \frac{1}{2}
\end{array} \right. \to \left[ \begin{array}{l}
\frac{{ - 1}}{{\sqrt x + 1}} = \frac{1}{2}\\
\frac{{ - 1}}{{\sqrt x + 1}} = - \frac{1}{2}
\end{array} \right.\\
\to \left[ \begin{array}{l}
- 2 = \sqrt x + 1\\
2 = \sqrt x + 1
\end{array} \right. \to \left[ \begin{array}{l}
\sqrt 3 = - 3\left( {vô lí} \right)\\
x = 1\left( l \right)
\end{array} \right.
\end{array}\)
⇒ Không tồn tại x TMĐK
