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MathGroup Archive 1997

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Re: Simplifying Ploynomials

  • To: mathgroup at smc.vnet.net
  • Subject: [mg5672] Re: Simplifying Ploynomials
  • From: hanson at physics.auburn.edu (James D Hanson)
  • Date: Tue, 7 Jan 1997 11:22:47 -0500
  • Organization: Auburn University Physics
  • Sender: owner-wri-mathgroup at wolfram.com

In article <5ap4ni$kv2 at dragonfly.wolfram.com>,
Ersek_Ted%PAX1A at mr.nawcad.navy.mil wrote:

> Dear Math Group,
> 
> The two polynomials "messy" and "clean" below are equivalentl.
> 
> messy = c0 + a*c1 - b*c1 + a^2*c2 - 2*a*b*c2 + b^2*c2
> 
> clean = c0 + c1(a-b) + c2(a-b)^2
> 
> If I get a polynomial like the messy one, how can I get Mma
> to convert is to the clean polynimial.
> 
> I don't yet have Version 3..0.
> Using Collect and Factor in version 2.2 does no good.
> Maybe FullSimplify in version 3.0 will work.
> 
> Still I would like to do this without using FullSimplify,
> because it can take a very long time.
> 
> Please Help
>              T.E.

It is not very elegant, but it works.

In[1]:=
messy = c0 + a*c1 - b*c1 + a^2*c2 - 2*a*b*c2 + b^2*c2
Out[1]=
                    2                  2
c0 + a c1 - b c1 + a  c2 - 2 a b c2 + b  c2
In[2]:=
clean = Expand[messy /. a -> x + b] /. x -> a - b
Out[2]=
                         2
c0 + (a - b) c1 + (a - b)  c2

-- 
James D. Hanson                          ph. (334) 844-5044
Department of Physics                    fax (334) 844-4613
206 Allison Laboratory
Auburn University, AL 36849-5311         hanson at physics.auburn.edu


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