After looking for the asymptotes of the function:
I found the answers y=0, y=-x-1 and y=x+1. This is almost exact: the last one should actually be y=x-1.
To find the result, I substituted x=my+c in the equation, which yielded $m=\pm 1$ and $c=\mp 1$, when c should be only -1. I can't find where I made a mistake. Any idea?