ta có pt hđgđ
\(-x^2=mx-1\)
\(\Leftrightarrow x^2+mx-1=0\)
\(\Delta=m^2+4>0\)
theo vi-ét ta có
\(\left\{{}\begin{matrix}x_1+x_2=-m\\x_1x_2=-1\end{matrix}\right.\)
\(x^2_1x_2+x_1x_2^2-x_1x_2=3\)
\(\Leftrightarrow x_1x_2\left(x_1+x_2-1\right)=3\)
\(\Rightarrow m=2\)