Quadratic equation

A Quadratic equation is an equation in which an independent variable appears with an exponent of two and no higher exponent. For example,

• 0 = 2 + 3x + 5x²

A quadratic equation has two roots (i.e. solutions).

The roots of quadratic equation a x² + b x + c = 0 whose coefficients are real numbers may be categorised as follows:

• If b² > 4 a c the roots are real, but different.
• If b² = 4 a c the roots are real, and equal.
• If b² < 4 a c the roots are [complex conjugate]? pairs (i.e. one root is y + i z, the other y - i z, where i is the complex number which satisfies i² = -1