       Re: infuriating Series[] question

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

```In a message dated 4/26/99 5:19:34 AM, psalzman at landau.ucdavis.edu writes:

>I'm trying to develop very high order difference equations, and want to
>use
>Mathematica to save me from calculating tons of quantities like 5^10 /
>7!
>
>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''''' * (5 x)^(10) / 10!
>
>The whole point in using Mathematica is so that I don't have to calculate
>things
>which look like 5^10 / 10!   (that's factorial, of course, not me being
>emphatic).
>
>Even when I try things like // Simplify or // FullSimplify, Mathematica
>refuses to
>simplify these rational coefficients.   One thing I've learned is that
>Mathematica
>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?
>

Pete,

Try this:

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

g[5*h]

g[10*h]

g

Bob Hanlon

```

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