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In algebra, a quadratic function, a quadratic polynomial, a polynomial of degree 2, or simply a quadratic, is a polynomial function in one or more variables in which the highest-degree term is of the second degree. For example, a quadratic function in three variables ''x'', ''y,'' and ''z'' contains exclusively terms ''x''2, ''y''2, ''z''2, ''xy'', ''xz'', ''yz'', ''x'', ''y'', ''z'', and a constant: : with at least one of the coefficients ''a, b, c, d, e,'' or ''f'' of the second-degree terms being non-zero. A ''univariate'' (single-variable) quadratic function has the form〔(【引用サイトリンク】 title=Quadratic Equation -- from Wolfram MathWorld )〕 : in the single variable ''x''. The graph of a univariate quadratic function is a parabola whose axis of symmetry is parallel to the -axis, as shown at right. If the quadratic function is set equal to zero, then the result is a quadratic equation. The solutions to the univariate equation are called the roots of the univariate function. The bivariate case in terms of variables ''x'' and ''y'' has the form : with at least one of ''a, b, c'' not equal to zero, and an equation setting this function equal to zero gives rise to a conic section (a circle or other ellipse, a parabola, or a hyperbola). In general there can be an arbitrarily large number of variables, in which case the resulting surface is called a quadric, but the highest degree term must be of degree 2, such as ''x''2, ''xy'', ''yz'', etc. ==Etymology== The adjective ''quadratic'' comes from the Latin word ''quadrātum'' ("square"). A term like is called a square in algebra because it is the area of a ''square'' with side . In general, a prefix quadr(i)- indicates the number . Examples are quadrilateral and quadrant. ''Quadratum'' is the Latin word for square because a square has four sides. 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 function」の詳細全文を読む スポンサード リンク
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