Re: Question: numerical solution of nonlinear differential equation

*To*: mathgroup at smc.vnet.net*Subject*: [mg26403] Re: [mg26390] Question: numerical solution of nonlinear differential equation*From*: "Carl K. Woll" <carlw at u.washington.edu>*Date*: Wed, 20 Dec 2000 00:21:29 -0500 (EST)*References*: <200012160740.CAA05212@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Ronald, I tried out your problem and it seems to work for some random values of the constants. In[8]:= NDSolve[{2 y''[x] + 3 y'[x] + 4 Exp[-5 x]==0, y'[0]==0, y'[1]==0},y,{x,0,1}] produces an error message about RowReduce, but it also produces an answer. A problem with the input in your post is that you had y[x]' instead of y'[x]. Also, it is not wise to use capital letters as arbitrary constants, as many of them have a special meaning in Mathematica. For example, D is the differentiation function, and E=2.7818... is the exponential constant e. You should also realize that Mathematica's NDSolve can only solve a single linear boundary value ODE. Carl Woll Physics Dept U of Washington ----- Original Message ----- From: "Ronald Sastrawan" <sastra at fmf.uni-freiburg.de> To: mathgroup at smc.vnet.net Subject: [mg26403] [mg26390] Question: numerical solution of nonlinear differential equation > > Hello ! > > I encountered a problem, trying to numerically solve a differential > equation. > My equation looks like: > > A y''[x] - B y[x]' + C Exp[-Dx] == 0 > with boundary conditions: y'[0]==0 , y'[E]==0 > > All constants A to E are known. > > Mathematica complains, that the equation is not linear. But in the > online documentation I saw many examples of nonlinear differential > equations, which all work fine. What is the difference between the > examples and my equation ? And is there a possibility to NDSolve my > equation ? > > Any hint on this would be of great help to me. > > Thanks a lot, > > Ronald > > -- > Ronald Sastrawan > > Freiburg Materials Research Center > Stefan-Meier-Str. 21 > D-79104 Freiburg > Germany > Tel: ++49/761/203-4802 > FAX: ++49/761/203-4801 > EMAIL: sastra at fmf.uni-freiburg.de > http://www.fmf.uni-freiburg.de/~biomed/FSZ/forschung-FSZ.html > > >

**References**:**Question: numerical solution of nonlinear differential equation***From:*Ronald Sastrawan <sastra@fmf.uni-freiburg.de>