\(\Delta=1-m+3=4-m\)
Để pt có ng0 thì \(\Delta\ge0\)\(\Rightarrow m\le4\)
Theo hệ thức Viet: \(x_1+x_2=2;x_1x_2=m-3\)
\(x_1\left(x_1+x_2\right)-2x_2=12\)
\(\Leftrightarrow x_1-x_2=6\)
Có hpt:\(\left\{{}\begin{matrix}x_1+x_2=2\\x_1-x_2=6\end{matrix}\right.\)\(\Rightarrow\left\{{}\begin{matrix}x_1=4\\x_2=-2\end{matrix}\right.\)
\(\Rightarrow x_1x_2=-8=m-3\Leftrightarrow m=-5\)(TM)