A polynomial equation in which the highest power of the variable is two. The general form of such equations in the variable x isax^{2} + bx + c = 0

where a, b and c are constants.

Generally, there are two values of x that can satisfy the equation, and they are:

In the Cartesian coordinate, the graph of a quadratic function y = ax^{2} + bx + c is a parabola. The solutions x_{1} and x_{2} represent the points where the graph crosses the x-axis. If the graph crosses the axis twice, there are two real distinct roots. If the graph touches the x-axis at one point, the two roots are equal. If the graph does not cross the x-axis at all, there are no real roots. In this case, the discriminant is negative, and the roots are two conjugate complex numbers.