quadratic, mathematical expression of the second degree in one or more unknowns (see polynomial ). The general quadratic in one unknown has the form ax 2+ bx + c, where a, b, and c are constants and x is the variable. A quadratic equation ax 2+ bx + c =0 always has two roots , not necessarily distinct these may be real or complex (see number ). The quadratic formula gives the roots of any quadratic equation in terms of its coefficients a, b, and c. The expression b 2−4 ac is called the discriminant and vanishes when the two roots coincide. If a, b, and c are real and the discriminant is not less than zero, the roots are real.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

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