Re: Problem with DSolve
- To: mathgroup at smc.vnet.net
- Subject: [mg96465] Re: Problem with DSolve
- From: Peter Breitfeld <phbrf at t-online.de>
- Date: Sat, 14 Feb 2009 03:08:54 -0500 (EST)
- References: <gn3bnf$pt9$1@smc.vnet.net>
Tony wrote:
> 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. >>
>
If you avoid using Reals you will still get the warning Solve::ifun, but
not {} as result
DSolve[{y'[x] == 1/5*y[x] - y[x]^2, y[0] == a}, y[x], x]
^^^
During evaluation of In[29]:= Solve::ifun: Inverse functions are being
used by Solve, so some solutions may not be found; use Reduce for
complete solution information. >>
Out[29]= {{y[x] -> (a E^(x/5))/(1 - 5 a + 5 a E^(x/5))}}
GruÃ? Peter
--
_________________________________________________________
Peter Breitfeld, Bad Saulgau --- http://www.pBreitfeld.de