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.