Re: Solving stiff differential equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg84501] Re: Solving stiff differential equations*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Sat, 29 Dec 2007 20:03:27 -0500 (EST)*References*: <fl4utf$9vb$1@smc.vnet.net>

Hi, scale the x[t] value to y[t]=x[t]/M ?? Regards Jens dkjk at bigpond.net.au wrote: > Hi all, > > I want to solve the following nonlinear ODE > > x'[t] == M - 3 x[t] Sqrt[-M*t + 7/10 + x[t]] > > x[0] == 3/10 > > where M is a very large number (~10^43). > > I tried solving this using > > M = 10^43; > s = NDSolve[{x'[t] == M - 3 x[t] Sqrt[-M t + 7/10 + x[t]], > x[0] == 3/10}, x[t], {t, -10, 10}, WorkingPrecision -> 20] > Plot[Evaluate[x[t] /. s], {t, -10, 10}, PlotRange -> All] > > but I got a lot of errors. Could anyone please advise how I should go > about solving this? > > Best regards, > James >