pt co nghiem nguyen khi \(\Delta \) la SCP
\(\Delta=\left(-\left(m+4\right)\right)^2-4\cdot2m\)
\(=m^2+8m+16-8m=m^2+16>0\forall m\)
Dat \(m^2+16=a^2\left(a\in Z\right)\)
\(\Leftrightarrow\left(a-m\right)\left(a+m\right)=16\)
\(\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}m=0\\a=\pm4\end{matrix}\right.\\\left\{{}\begin{matrix}m=\pm3\\a=\pm5\end{matrix}\right.\end{matrix}\right.\)