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MathGroup Archive 2010

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Collecting Positive and Negative Terms

  • To: mathgroup at smc.vnet.net
  • Subject: [mg111700] Collecting Positive and Negative Terms
  • From: Michael Knudsen <micknudsen at gmail.com>
  • Date: Wed, 11 Aug 2010 04:44:17 -0400 (EDT)

Hi,

I'm currently doing calculations often involving very large
expressions with a lot of unknown parameters. To investigate whether
an expression is positive or negative, I usually expand it using the
Expand command and manually copy and paste the positive and negative
terms into new expressions and simplify them using FullSimplify. In my
case it often turns out that comparing the two is much easier than
looking at the entire expression as a whole.

However, it's very cumbersome to do all this manually. Is there an
easy way in Mathematica to pick out terms begging with + (or -) in a
sum?

Thanks,
Michael Knudsen


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