a) không vì \(\left(d\right)\equiv\left(d'\right)\) \(\Leftrightarrow\left\{{}\begin{matrix}m+2=m^2+2m\\1=-1\end{matrix}\right.\) (vô lí)
b) để \(\left(d\right)\backslash\backslash\left(d'\right)\Leftrightarrow m^2+2m=m+2\)
\(\Leftrightarrow m^2+m-2=0\Leftrightarrow\left[{}\begin{matrix}m=1\\m=-2\end{matrix}\right.\) vậy \(m=1;m=-2\)