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Re: How to select terms wanted in a series

• To: mathgroup at smc.vnet.net
• Subject: [mg85957] Re: [mg85916] How to select terms wanted in a series
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Thu, 28 Feb 2008 02:59:25 -0500 (EST)
• Reply-to: hanlonr at cox.net

Cases[expression, x*y*_.]


Bob Hanlon

---- Barrow <GRseminar at gmail.com> wrote: 
> 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
>