Giải thích các bước giải:
$\dfrac{m + 1}{m - 1} \geq 0$
$\Leftrightarrow \left[ \begin{array}{l}\left\{\begin{matrix}m + 1 \geq 0\\ m - 1 > 0\end{matrix}\right.\\\left\{\begin{matrix}m + 1 \leq 0\\ m - 1 < 0\end{matrix}\right.\end{array} \right.$
$\Leftrightarrow \left[ \begin{array}{l}\left\{\begin{matrix}m \geq -1\\ m > 1\end{matrix}\right.\\\left\{\begin{matrix}m \leq -1\\ m < 1\end{matrix}\right.\end{array} \right.$
$\Leftrightarrow \left[ \begin{array}{l}m > 1\\m \leq -1\end{array} \right.$
