\(y'=-3x^2+2.\left(2m-1\right).x-\left(2-m\right)\)
\(\Delta y'=\left[2\left(2m-1\right)\right]^2-4.\left(-3\right).\left[-\left(2-m\right)\right]\)
= \(4.\left(4m^2-4m+1\right)+12.\left(m-2\right)\)
= \(16m^2-16m+4+12m-24\)
= \(16m^2-4m-20\)
\(\Delta>0\Leftrightarrow16m^2-4m-20>0\Leftrightarrow\left\{{}\begin{matrix}m< -1\\m>1,25\end{matrix}\right.\)