Re: Is this solvable using Mathematica?

*To*: mathgroup at smc.vnet.net*Subject*: [mg99075] Re: Is this solvable using Mathematica?*From*: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>*Date*: Sun, 26 Apr 2009 01:38:40 -0400 (EDT)*References*: <gsuiqn$dq8$1@smc.vnet.net>

One problem is that d doesn't have a value... On Apr 25, 10:49 am, johnboy98... at yahoo.com wrote: > Supposed you want to define a second order derivative along with your > ODEs. (So you can scale the second order term) > > Example shown below. > > k1 = 1; > r1 = 1; > NDSolve[{a'[t] == k1 b[t] - d, a''[t] == r1 b'[t], a'[0] == 0= , a[0] == > 1, b[0] == 0}, {a[t], b[t]}, {t, 1, 10} ] > > But I get an error. > > NDSolve::ntdvmm: > Cannot solve to find an explicit formula for the derivatives. NDSolve > will try solving the system using a mass matrix method. > > NDSolve::ndnum: Encountered non-numerical value for a derivative at t > == 0.`. > > Maybe this is more of a math question than software. But I would be > very interested in seeing if it's doable in Mathematica. > > Thanks in advance.