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MathGroup Archive 1999

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Re: O.D.E in Power Series

  • To: mathgroup at smc.vnet.net
  • Subject: [mg18276] Re: O.D.E in Power Series
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Fri, 25 Jun 1999 15:05:22 -0400
  • Organization: Universitaet Leipzig
  • References: <7ku0dk$9a1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Alan,

if you want a general infinite power series you should try
the SpecialFunction.m package from MathSource.
If a solution to the first order terms is sufficient
for you than

deqn=y''[x]-2(x+3)y'[x]-3y[x]==0;
order=10;
Solve[LogicalExpand[
    deqn /.Thread[ {#,D[#,x],D[#,{x,2}]} & /@ (
            y[x]->Sum[a[i]*x^i,{i,0,order}]+O[x]^(order+1))]],
  Table[a[i],{i,2,order}]]

will do it.

Regards
  Jens

ALAN S BLOOM wrote:
> 
> I am trying to solve this equation below:
> y''-2(x+3)y'-3y=0 with the DSolve command.
> 
> DSolve [y''[x]-2(x+3)y'[x]-3y[x]==0,y[x],x]
> 
> How can I make it work?
> 
> Alan


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