\[\begin{array}{l}
2{\sin ^2}x + \left( {m + 2} \right)\sin x + 2m - 4 = 0\\
\Leftrightarrow \left( {\sin x - 2} \right)\left( {2\sin x + m - 2} \right) = 0\\
\Leftrightarrow \left[ \begin{array}{l}
\sin x = 2\left( {VN} \right)\\
\sin x = \frac{{2 - m}}{2}
\end{array} \right.\\
PT\,co\,nghiem \Leftrightarrow - 1 \le \frac{{2 - m}}{2} \le 1 \Leftrightarrow - 2 \le 2 - m \le 2 \Leftrightarrow 0 \le m \le 4
\end{array}\]
