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  • Numerator[ expr ] gives the numerator of expr.
  • Numerator picks out terms which do not have superficially negative exponents. Denominator picks out the remaining terms.
  • An exponent is "superficially negative" if it has a negative number as a factor.
  • The standard representation of rational expressions as products of powers means that you cannot simply use Part to extract numerators.
  • Numerator can be used on rational numbers.
  • See the Mathematica book: Section 1.4.6.
  • See also: ExpandNumerator.

    Further Examples

    See the Further Examples for Denominator.