Re: DSolve solution validation

*To*: mathgroup at smc.vnet.net*Subject*: [mg33939] Re: DSolve solution validation*From*: Gerhard Wesp <gwesp at cosy.sbg.ac.at>*Date*: Wed, 24 Apr 2002 01:21:45 -0400 (EDT)*Organization*: Department of Computer Science, Salzburg University*References*: <aa3fm7$7pl$1@smc.vnet.net>*Reply-to*: gwesp at cosy.sbg.ac.at*Sender*: owner-wri-mathgroup at wolfram.com

Vladimir Bondarenko <vvb at mail.strace.net> wrote: > DSolve[y'[z] == Abs[y[z]], y[z], z] this is a good example where the built-in human DSolve works better than Mathematica's :-) y'=abs(y) has the solution y = C e^z. depending on the sign of C, y is either always positive or always negative. regards, -gerhard