Neither of which should pose a problem.
I'm going to assume that you wrote it wrong and meant:
<-- Square both sides
which you can solve using the quadratic formula:
The bad news is that whenever you square both sides of an equation you should always check to make sure you haven't added a new solution and these forms are messy to substitute back into the original equations. I'll give you peace of mind by telling you that only the "+" solution is correct.