Re: Problem with DSolve

*To*: mathgroup at smc.vnet.net*Subject*: [mg96461] Re: [mg96410] Problem with DSolve*From*: "David Park" <djmpark at comcast.net>*Date*: Sat, 14 Feb 2009 03:08:10 -0500 (EST)*References*: <8204467.1234516287118.JavaMail.root@m02>

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. >>