ta có : \(\dfrac{m-2}{m+1}< 0\Rightarrow\left\{{}\begin{matrix}\left\{{}\begin{matrix}m-2>0\\m+1< 0\end{matrix}\right.\\\left\{{}\begin{matrix}m-2< 0\\m+1>0\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}\left\{{}\begin{matrix}m>2\\m< -1\end{matrix}\right.\\\left\{{}\begin{matrix}m< 2\\m>-1\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}m\in\varnothing\\-1< m< 2\end{matrix}\right.\) vậy \(-1< m< 2\) thì \(\dfrac{m-2}{m+1}< 0\)
