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:''For the case of more than one variable, see Conic section or Quadratic form.'' In elementary algebra, a quadratic equation (from the Latin ''quadratus'' for "square") is any equation having the form : where represents an unknown, and , , and represent known numbers such that is not equal to . If , then the equation is linear, not quadratic. The numbers , , and are the ''coefficients'' of the equation, and may be distinguished by calling them, respectively, the ''quadratic coefficient'', the ''linear coefficient'' and the ''constant'' or ''free term''.〔Protters & Morrey: " Calculus and Analytic Geometry. First Course"〕 Because the quadratic equation involves only one unknown, it is called "univariate". The quadratic equation only contains powers of that are non-negative integers, and therefore it is a polynomial equation, and in particular it is a second degree polynomial equation since the greatest power is two. Quadratic equations can be solved by a process known in American English as factoring and in other varieties of English as ''factorising'', by completing the square, by using the quadratic formula, or by graphing. Solutions to problems equivalent to the quadratic equation were known as early as 2000 BC. ==Solving the quadratic equation== A quadratic equation with real or complex coefficients has two solutions, called ''roots''. These two solutions may or may not be distinct, and they may or may not be real. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Quadratic equation」の詳細全文を読む スポンサード リンク
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