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In mathematics, a rational function is any function which can be defined by a rational fraction, ''i.e.'' an algebraic fraction such that both the numerator and the denominator are polynomials. The coefficients of the polynomials need not be rational numbers, they may be taken in any field ''K''. In this case, one speaks of a rational function and a rational fraction ''over K''. The values of the variables may be taken in any field ''L'' containing ''K''. Then the domain of the function is the set of the values of the variables for which the denominator is not zero and the codomain is ''L''. By modifying the definition to use equivalence classes the set of rational functions becomes a field. ==Definitions== A function is called a rational function if and only if it can be written in the form : where and are polynomials in and is not the zero polynomial. The domain of is the set of all points for which the denominator is not zero. However, if and have a non constant polynomial greatest common divisor , then setting and produces a rational function : which may have a larger domain than , and is equal to on the domain of It is a common usage to identify and , that is to extend "by continuity" the domain of to that of Indeed, one can define a rational fraction as an equivalence class of fractions of polynomials, where two fractions ''A''(''x'')/''B''(''x'') and ''C''(''x'')/''D''(''x'') are considered equivalent if ''A''(''x'')''D''(''x'')=''B''(''x'')''C''(''x''). In this case is equivalent to . 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「Rational function」の詳細全文を読む スポンサード リンク
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