Solving stiff differential equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg84490] Solving stiff differential equations*From*: dkjk at bigpond.net.au*Date*: Sat, 29 Dec 2007 02:58:31 -0500 (EST)

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