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Re: infuriating Series[] question

  • To: mathgroup at
  • Subject: [mg17275] Re: [mg17226] infuriating Series[] question
  • From: BobHanlon at
  • Date: Fri, 30 Apr 1999 02:34:52 -0400
  • Sender: owner-wri-mathgroup at

In a message dated 4/26/99 5:19:34 AM, psalzman at writes:

>I'm trying to develop very high order difference equations, and want to
>Mathematica to save me from calculating tons of quantities like 5^10 /
>If I define:
>   g[x_] := Series[ f[x], {x,0,10} ]
>And try to compute stuff like:
>   g[5*h] or g[10*h]
>It gives me the right answer, but i get terms like
>   f'''''[0] * (5 x)^(10) / 10!
>The whole point in using Mathematica is so that I don't have to calculate
>which look like 5^10 / 10!   (that's factorial, of course, not me being
>Even when I try things like // Simplify or // FullSimplify, Mathematica
>refuses to
>simplify these rational coefficients.   One thing I've learned is that
>can do anything -- but figuring out how to do the something is often
>completely not obvious to a nominal user like me.
>Can someone tell me the secret here?


Try this:

g[x_] := Module[{t}, Normal[Series[ f[t], {t,0,10} ] ]/. t -> x]




Bob Hanlon

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