Re: collect derivatives

*To*: mathgroup at smc.vnet.net*Subject*: [mg23305] Re: [mg23259] collect derivatives*From*: BobHanlon at aol.com*Date*: Mon, 1 May 2000 18:00:07 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

In a message dated 4/29/2000 10:20:20 PM, robert.schuerhuber at gmx.at writes: >is there a way to use "collect[]" to collect all terms with a specific >derivative, e.g. to produce something like > >z''[x] u[x] + z'[x] (u'[x]+u[x]) + z[x] > I believe that this would be case-specific; however, for the example that you gave expr = (z''[x] u[x] + z'[x] (u'[x] + u[x]) + z[x] // Expand); expr // Simplify z[x] + u'[x]*z'[x] + u[x]*(z'[x] + z''[x]) expr // FullSimplify z[x] + (u[x] + u'[x])*z'[x] + u[x]*z''[x] Bob BobHanlon at aol.com