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MathGroup Archive 2005

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Re: coding problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60183] Re: coding problem
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Tue, 6 Sep 2005 05:28:48 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, U.K.
  • References: <dfj9bg$rfm$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Ming Hong wrote:
> I am trying to solve the following equations:
> 
> xy''+(1+x)y'=0
> xy'(0)=-1/2
> y(Infinity)=0
> 
> Here is what I put into Mathematica:
> 
> Dsolve[{x*y''[x]+(1+x)*y'[x]==0,x*y'[0]==-1/2,y[Infinity]==0},y,x]
> 
> It didn't work and I can not figure out why.
> 
> Thanks for your help!
> 
> Ming
> 
Hi Ming,

*DSolve* must be written with a capital "D" _and_ a capital "S".

Nevertheless, it seems that your equation do not have a solution for the 
given conditions.

In[1]:=
DSolve[{x*Derivative[2][y][x] + (1 + x)*Derivative[1][y][x] == 0, 
x*Derivative[1][y][0] == -2^(-1),
    y[Infinity] == 0}, y, x]

Divide::infy: Infinite expression 1/0 encountered.

DSolve::bvnul: For some branches of the general solution, the given 
boundary conditions lead to an empty solution. More...

Out[1]=
{}

In[4]:=
$Version

Out[4]=
"5.2 for Microsoft Windows (June 20, 2005)"

Best regards,
/J.M.


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