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MathGroup Archive 2000

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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


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