I find that having the (-) on the x^{2} can sometimes make the quadratic formula confusing, as having the correct sign on the a,b, and c values is critical to get the correct answer. Multiply the whole equation by -1 and give the quadratic equation
another shot!
The discriminant: b^{2 }- 4*a*c is also a very helpful tool for solving polynomials.
Hope this helps!