-4m - 4 = 4m
$$\begin{array}{rll} -4m - 4 &=& 4m\\ -4m +4m- 4 &=& 4m+4m\\ - 4 &=&8m\\ - 4/8 &=&8m/8\\ - 1/2 &=&m\\ m&=&\frac{-1}{2} \end{array}$$