What is Quadratic Equation?

The roots are given by the quadratic formula $x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}$. The expression under the root, $D = b^2 - 4ac$, is the discriminant. If $D > 0$ there are two distinct real roots. If $D = 0$ there is one repeated root. If $D < 0$ there are no real roots. The roots can also be found by factorising or by completing the square.