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MathGroup Archive 2002

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Re: How to pick all terms which have are multiplied with a factor, e.g., 2

  • To: mathgroup at smc.vnet.net
  • Subject: [mg35466] Re: How to pick all terms which have are multiplied with a factor, e.g., 2
  • From: Andrzej Kozlowski <andrzej at bekkoame.ne.jp>
  • Date: Sun, 14 Jul 2002 06:19:38 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

I guess the simples way is something like


In[8]:=
2*a*b^2*c^3 + 13*x*y*a*b + 2/d //. 2*x_ + 2*y_ -> 2*(x + y)

Out[8]=
2*(a*b^2*c^3 + 1/d) + 13*a*b*x*y



The reason for ReplaceRepeated (//.) is that this will work with more 
multiples of 2, e.g.

In[9]:=
2*a*b^2*c^3 + 13*x*y*a*b + 2/d + 2*h + 2*x^2*y^3 //.
   2*x_ + 2*y_ -> 2*(x + y)

Out[9]=
13*a*b*x*y + 2*(a*b^2*c^3 + 1/d + h + x^2*y^3)


Andrzej Kozlowski
Toyama International University
JAPAN
http://platon.c.u-tokyo.ac.jp/andrzej/


On Saturday, July 13, 2002, at 04:49  PM, Matthias G. Imhof wrote:

> I would like to simplify a large symbolic summation. I know that terms 
> which
> are multiplied with a common integer factor can ultimately be combined 
> and
> simplified.
>
> As an example: from the sum
>
> 	2 a b^2 c^3 + 13 x y a b + 2 d^-1
>
> I would like to pick 2 a b^2 c^3 + 2 d^-1 to combine them; and 
> similarly for
> other common integer factors. I suspect that patterns would help, but I 
> did
> not manage to devise a correct one.
>
> Matthias
>
>
>
>
Andrzej Kozlowski
Toyama International University
JAPAN
http://platon.c.u-tokyo.ac.jp/andrzej/



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