Re: differential equation solve

*To*: mathgroup at smc.vnet.net*Subject*: [mg68847] Re: [mg68821] differential equation solve*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Mon, 21 Aug 2006 03:27:46 -0400 (EDT)*Reply-to*: hanlonr at cox.net*Sender*: owner-wri-mathgroup at wolfram.com

Make sure that all of your variables are clear $Version 5.2 for Mac OS X (June 20, 2005) Clear[x,y,t]; DSolve[{y'[x] == r*y[x], y[0] == a}, y, x] {{y -> Function[{x}, a*E^(r*x)]}} DSolve[{y'[x] == r*y[x], y[0] == a}, y[x], x] {{y[x] -> a*E^(r*x)}} Off[Solve::ifun]; DSolve[{x'[t] == r*x[t]*(1 - x[t]/xm), x[0] == x0}, x, t] {{x -> Function[{t}, (E^(r*t)*x0*xm)/(E^(r*t)*x0 - x0 + xm)]}} DSolve[{x'[t] == r*x[t]*(1 - x[t]/xm), x[0] == x0}, x[t], t] {{x[t] -> (E^(r*t)*x0*xm)/(E^(r*t)*x0 - x0 + xm)}} Bob Hanlon ---- elvis <rapstone at gmail.com> wrote: > Here we often use mathematica to solve differential equations, when I > encouter a equation with several constrains I set them to those values. > But it cannot solve it and have the following warnings: > > DSolve::deqx: Supplied equations are not differential equations of > the given functions. > > Give a very simple differential equation here: > > DSolve[{y'[x] == r*y[x], y[0] == a}, y, x] > > another equation: > > \!\(DSolve[{\(x'\)[t] == r*x[t] \((1 - x[t]\/xm)\), x[0] == x0}, x, > t]\) > > this face anothe prolbem > > Can anyone help to "solve" this problem for me? > Thanks! >