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How to select terms wanted in a series

  • To: mathgroup at smc.vnet.net
  • Subject: [mg85916] How to select terms wanted in a series
  • From: Barrow <GRseminar at gmail.com>
  • Date: Wed, 27 Feb 2008 04:33:57 -0500 (EST)

Dear all,

I have an expression, which is a sum of large number of terms, e.g.

expression = x + 2x*y - x*y*z + u*x*y + 3u^2

And I want to select out terms with the factor (x*y). e.g.

The terms in "expression" that I want are 2x*y, -x*y*z, u*x*y

My first step is,

allterms = Apply[List, expression]

Then, I don't know how to extract the terms I want, I use

Select[allterms, (# == x*y*_)&]

But It doesn't work.

Anyone has some good ideas? any help will be appreciated much!
Sincerely  Barrow


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