You need to show your whole equation.  The actual value of $h$ for $h^2=1$ in this question is $h=-1$.  No matter what method is used, it should end up with a quadratic equation $h^2 - 5h - 6=0$. My guess is that at some places you did a squaring of something, which brought in the extraneous solutions like $h=1$ and $h=-6$.