I agree with @gasman and @LostInParadise. I will tell you general rule. You need to re-arrange any quadratic equation in this format, and put values of the corresponding constants.
General form of a quadratic equation : ax^2 + bx + c = 0
Two values of x are :
x = [- b +/- Square root (b^2 – 4ac)] / (2a) ...use +/- to get two values
If the equation is relatively simpler, use factorization method as @LostInParadise has shown. Personally, I will use factorization when constants a,b,c are integers. In other cases, it is more easier to find roots using the above formula.
Generally, you will get as many number of values for x, the variable, as the highest degree in the equation. For quadratic equation, the highest degree is two, so you can get two values for x. For cubic equation, there will be three values for x, and so on.