Complete the square to solve the general quadratic equation ax2+bx+c=0 to obtain
x=2a−b±b2−4ac.
The discriminant of the quadratic equation Δ=b2−4ac determines the nature of the solutions of the equation. If Δ>0, the equation has two distinct real solutions. If Δ=0, the equation has a single repeated real root. If Δ<0, there are two distinct imaginary solutions.