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smart change of variables?

• To: mathgroup at smc.vnet.net
• Subject: [mg87695] smart change of variables?
• From: Barrow <GRseminar at gmail.com>
• Date: Tue, 15 Apr 2008 06:51:07 -0400 (EDT)

Dear all,

I have a arithmetic problem.
I have an expression expr = (p1 + 2*p2)*(k1 + 2*k2)
where p1 + p2 = k1 + k2
I wanna make the following change of variables,
s = (p1 + p2)^2
t = (p1 - k1)^2
u = (p1 - k2)^2

Is it possible to tell Mathematica to express expr
in terms of s, t, and u automatically?

Thanks so much.
any ideas would be appreciated.
Sincerely Barrow

• Follow-Ups:
  • Re: smart change of variables?
    • From: Daniel Lichtblau <danl@wolfram.com>
  • Re: smart change of variables?
    • From: "W_Craig Carter" <ccarter@mit.edu>