Để hàm số xác định :
\(mx^2-mx+m+3\ge0\)
\(\Leftrightarrow\left\{{}\begin{matrix}\Delta\ge0\\m>0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}m>0\\m^2-4m\left(m+3\right)\ge0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}m>0\\-3m^2-12m\ge0\end{matrix}\right.\)