Re: Question: numerical solution of nonlinear differential equation

*To*: mathgroup at smc.vnet.net*Subject*: [mg26413] Re: Question: numerical solution of nonlinear differential equation*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Wed, 20 Dec 2000 00:21:36 -0500 (EST)*Organization*: Universitaet Leipzig*References*: <91f7n8$556@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, a) the equatio should be written with y'[x] and *not* with y[x]' ! b) In[]:=deqn = A y''[x] - B y'[x] + C Exp[-D*x] == 0; sol = y[x] /. First[DSolve[deqn, y[x], x]]; In[]:=sol /. Solve[{sol == 0 /. x -> 0, sol == 0 /. x -> E}, {C[1], C[2]}] // FullSimplify Out[]={(C*(E^(D*E) - E^((B/A + D)*E) - E^(D*x) + E^((B/A + D)*x) + E^(D*(E + x))*(E^((B*E)/A) - E^((B*x)/A))))/ (D*(B + A*D)*E^(D*(E + x))*(-1 + E^((B*E)/A)))} c) NDSolve[] can't solve nonlinear boundary value problems, I don't know what you saw. Regards Jens Ronald Sastrawan wrote: > > 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 > --