Groups > comp.soft-sys.math.mathematica > #1799

Re: Simplify results

From	Gary Wardall <gwardall@gmail.com>
Newsgroups	comp.soft-sys.math.mathematica
Subject	Re: Simplify results
Date	2011-04-20 08:29 +0000
Organization	Steven M. Christensen and Associates, Inc and MathTensor, Inc.
Message-ID	<iom5hr$25$1@smc.vnet.net> (permalink)
References	<iojpot$i4q$1@smc.vnet.net>

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On Apr 19, 5:56 am, "Berthold Hamburger" <b-hambur...@artinso.com>
wrote:
> Hi,
>
> This might be a silly question, so please bear with me, but I have been
> scratching my head about it for some time now.
>
> Is there a particular reason why Mathematica (8.01) simplifies the following
> fraction reversing the signs in the result:
>
> IN:
>
> Simplify[(8a^2b^3(c^2+1)^4-6a^3b^2(c^2+1)^3+14a^4b
> (c^2+1)^2)/(4a^3b^2(c^2+1)^2-10a^4b^3(c^2+1)^3)]
>
> OUT:
>
> (-7 a^2+3 a b (1+c^2)-4 b^2 (1+c^2)^2)/(a b (-2+5 a b (1+c^2)))
>
> Reducing the fraction by hand gives me:
>
> (7 a^2-3 a b (1+c^2)+4 b^2 (1+c^2)^2)/(a b (2-5 a b (1+c^2)))
>
> Thanks
>
> Berthold
>
> --
>
> Berthold Hamburger - Cellist/Spain
>
> Email: beha...@artinso.com
>
> http://www.artinso.com
>
> http://www.astronomy.artinso.com

Berthold:

I got:

(-7 a^2 + 3 a b - 4 b^2 + 3 a b c^2 - 8 b^2 c^2 -
 4 b^2 c^4)/(-2 a b + 5 a^2 b^2 + 5 a^2 b^2 c^2)

by hand which is correct too, I think.

The point being there are many equivalent forms for mathematical
expressions. Mathematica would have to be clairvoyant to know which
form you would expect to expressions to simplify into.

Good Luck

Gary Wardall

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Thread

Simplify results "Berthold Hamburger" <b-hamburger@artinso.com> - 2011-04-19 10:56 +0000
  Re: Simplify results "Sjoerd C. de Vries" <sjoerd.c.devries@gmail.com> - 2011-04-20 08:28 +0000
  Re: Simplify results Gary Wardall <gwardall@gmail.com> - 2011-04-20 08:29 +0000

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