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MathGroup Archive 2000

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Re: Consrtaining Variables

  • To: mathgroup at smc.vnet.net
  • Subject: [mg26513] Re: [mg26508] Consrtaining Variables
  • From: BobHanlon at aol.com
  • Date: Sat, 30 Dec 2000 22:13:39 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

With version 4, try using assumptions with Simplify or FullSimplify

Simplify[Abs[a - x], x >= a]

x - a

Factor[Sum[Simplify[Abs[a - x], x >= a], {x, a, 10}]]

(1/2)*(a - 11)*(a - 10)

Sum[Simplify[Abs[a - x], {x >= a, a >= 5}], {x, 0, 10}]

6*a + Abs[a - 10] + Abs[a - 9] + Abs[a - 8] + Abs[a - 7] + 
  Abs[a - 6] - 15


Bob Hanlon

In a message dated 12/30/00 2:20:27 AM, frumple*NOSPAM* at home.com writes:

>I am working on a package where I need to constrain the domain of some
>
>variables to the non-negative integers. In particular I would like to be
>
>able for Mathematica to recognize that Abs[a-x] = x-a when x>=a where 
>the Abs term is in both the limits and kernal of a Sum.
>


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