\(\Rightarrow\left\{{}\begin{matrix}m^2x-2my=3m\\6x+2my=8\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left(m^2+6\right)x=3m+8\\6x+2my=8\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}x=\frac{3m+8}{m^2+6}\\y=\frac{4m-9}{m^2+6}\end{matrix}\right.\)
\(x>0;y< 0\Leftrightarrow\left\{{}\begin{matrix}\frac{3m+8}{m^2+6}>0\\\frac{4m-9}{m^2+6}< 0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3m+8>0\\4m-9< 0\end{matrix}\right.\) \(\Leftrightarrow-\frac{8}{3}< m< \frac{9}{4}\)
