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Re: Algebraic Manipulation

• To: mathgroup at smc.vnet.net
• Subject: [mg46172] Re: Algebraic Manipulation
• From: bobhanlon at aol.com (Bob Hanlon)
• Date: Tue, 10 Feb 2004 00:05:39 -0500 (EST)
• References: <c07p9h$kmc$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

expr=x*y*(-(z^2/(r^2*(x^2+y^2)))-1/(r*(k+r))+1/(x^2+y^2));

Simplify[expr, r^2==x^2+y^2+z^2]

(k*x*y)/(r^2*(k + r))


Bob Hanlon

In article <c07p9h$kmc$1 at smc.vnet.net>, "David Park" <djmp at earthlink.net>
wrote:

<< expr = x*y*(-(z^2/(r^2*(x^2 + y^2))) - 1/(r*(k + r)) + 1/(x^2 + y^2))

where

r^2 == x^2 + y^2 + z^2

reduces to

(k*x*y)/(r^2*(k + r))

I wonder if anyone can show an elegant or short method to do the
simplification?