Editing Indeterminate (variable) (section)

==Formal power series==
{{main|Formal power series}}
A [[formal power series]] in an indeterminate ''<math>X</math>'' is an expression of the form <math>a_0 + a_1X + a_2X^2 + \ldots</math>, where no value is assigned to the symbol ''<math>X</math>''.<ref>{{Cite web|url=http://mathworld.wolfram.com/FormalPowerSeries.html|title=Formal Power Series|last=Weisstein|first=Eric W.|website=mathworld.wolfram.com|language=en|access-date=2019-12-02}}</ref> This is similar to the definition of a polynomial, except that an infinite number of the coefficients may be nonzero. Unlike the [[power series]] encountered in calculus, questions of [[Convergence (mathematics)|convergence]] are irrelevant (since there is no function at play). So power series that would diverge for values of ''<math>x</math>'', such as ''<math>1 + x + 2x^2 + 6x^3 + \ldots + n!x^n + \ldots\,</math>'', are allowed.