Editing Quadratic function (section)

====Bivariate and multivariate cases====

Any quadratic polynomial with two variables may be written as
:<math>a x^2 + b y^2 + cxy + dx+ e y + f,</math>
where {{math|''x''}} and {{math|''y''}} are the variables and {{math|''a'', ''b'', ''c'', ''d'', ''e'', ''f''}} are the coefficients, and one of {{mvar|a}}, {{mvar|b}} and {{mvar|c}} is nonzero.  Such polynomials are fundamental to the study of [[conic section]]s, as the [[implicit equation]] of a conic section is obtained by equating to zero a quadratic polynomial, and the [[zero of a function|zeros]] of a quadratic function form a (possibly degenerate) conic section.

Similarly, quadratic polynomials with three or more variables correspond to [[quadric]] surfaces or [[hypersurface]]s. 

Quadratic polynomials that have only terms of degree two are called [[quadratic form]]s.