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Re: Problem with DSolve


Try an exact version of the equations. You still obtain a warning about
inverse functions, but you do obtain a solution.

Clear[y];
First@DSolve[{y'[x] == y[x]/50 - y[x]^2, y[0] == a}, y, x];
y[x_] = y[x] /. %
{y'[x] == y[x]/50 - y[x]^2, y[0] == a}

(a E^(x/50))/(1 - 50 a + 50 a E^(x/50))
{True, True}


David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/  


From: Tony [mailto:aezajac at optonline.net] 

can anyone help what is wrong?
On version 7 I enter

   DSolve[{y'[x]==.02*y[x]-y[x]^2,y[0]==a},y[x],x]

and get

       During evaluation of In[58]:= Solve::ifun: Inverse functions are
being used by Solve, so some solutions may not be  found; use Reduce for
complete solution information. >>
       During evaluation of In[58]:= Solve::ifun: Inverse functions are
being used by Solve, so some solutions may not be found; use Reduce for
complete solution information. >>
       During evaluation of In[58]:= DSolve::bvnul: For some branches of the
general solution, the given boundary conditions lead to an empty solution.
>>




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