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Re: signs in the mathematica output

• To: mathgroup at smc.vnet.net
• Subject: [mg92483] Re: signs in the mathematica output
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Wed, 1 Oct 2008 18:32:42 -0400 (EDT)
• Organization: Uni Leipzig
• References: <gbulqi$lcr$1@smc.vnet.net>
• Reply-to: kuska at informatik.uni-leipzig.de

Hi,

the problem can't be solved, because Mathematica orders sums
due to the complexity of the summands, the lowest complexity has
a single number and so -1 comes before a variable like "s" or "a".
Second your expression is

Times[Plus[1,Times[-1,s]],Plus[1,Times[-1,a]]

after FullSimplify[] it is

Times[Plus[-1,s],Plus[-1,a]]

and that is simpler than you input.

You can play around with the ExcludeForms and ComplexityFunction
options of FullSimplify[] but I would not expect that a general
solution exist.

Regards
   Jens

Simone Moriconi wrote:
> Hello everybody! I have a problem in using the Mathematica Package which is probably a bit stupid but very annoying when you have long expressions.. 
> 
> When I "FullSimplify" big equations, in the output the negative sign is always put aside i.e. if I do something like:
> 
> FullSimplify[(1-s)(1-a)]
> 
> I obtain 
> 
> (-1+s)(-1+a).
> 
> Which is very confusing with long and tedius expressions. Does anybody know a way to solve this problem?
> 
> Thanks a lot for your help!!
>