Lời giải
(Đk1) \(a\ne0\Rightarrow m\ne0\)
(Đk 2 ) \(\Delta'=\left(m+1\right)^2+2m\left(m+1\right)>0\)
\(\Leftrightarrow\left(m+1\right)\left(m+1+2m\right)>0\).
\(\Leftrightarrow\left(m+1\right)\left(3m+1\right)>0\Rightarrow\left[{}\begin{matrix}m< -1\\m>-\dfrac{1}{3}\end{matrix}\right.\)