View source for The Quadratic Formula

The quadratic formula is <math>\frac{-b\pm\sqrt{b^2-4ac}}{2a}.</math> This is used to find the roots of a quadratic, <math>ax^2+bx+c=0.</math> The part inside the square root, or <math>b^2-4ac</math> is called the discriminant<math>.</math> When the discriminant is equal to <math>0,</math> the quadratic only has one root<math>,</math> which is called a double root. If the discriminant is negative, the quadratic has two non<math>-</math>real roots<math>,</math> so the roots are complex<math>.</math> If the discriminant is positive<math>,</math> then the quadratic has two real roots.