In mathematics, a quadratic equation is a polynomial equation of the second degree. The general form is
where a ≠ 0. (For if a = 0, the equation becomes a linear equation.)
The letters a, b, and c are called coefficients: the quadratic coefficient a is the coefficient of x2, the linear coefficient b is the coefficient of x, and c is the constant coefficient, also called the free term or constant term.
Quadratic equations are called quadratic because quadratus is Latin for "square"; in the leading term the variable is squared.
A quadratic equation with real or complex coefficients has two (not necessarily distinct) solutions, called roots, which may or may not be real, given by the quadratic formula:
where the symbol "±" indicates that both
are solutions.