Definition:Quadratic Equation

Definition
A quadratic equation is a polynomial equation of the form:
 * $a x^2 + b x + c = 0$

such that $a \ne 0$.

From Solution to Quadratic Equation, the solutions are:
 * $x = \dfrac {-b \pm \sqrt {b^2 - 4 a c} } {2 a}$

Also defined as
Some older treatments of this subject present this as:


 * An algebraic equation of the form $a x^2 + 2 b x + c = 0$ is called a quadratic equation.


 * It has solutions:
 * $x = \dfrac {-b \pm \sqrt {b^2 - a c} } a$

but this approach has fallen out of fashion.

Also see

 * Solution to Quadratic Equation


 * Definition:Cubic Equation
 * Definition:Quartic Equation
 * Definition:Quintic Equation