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MathGroup Archive 2000

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Re: system of simultaneous equations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg22914] Re: system of simultaneous equations
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Thu, 6 Apr 2000 02:04:31 -0400 (EDT)
  • Organization: Universitaet Leipzig
  • References: <8ce9en$12i@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

let us make some equations:

eqn = {x^2 + y + z == 1,
             x + y^2 + z == 1,
            x + y + z^2 == 1}

solve it:

sol = Solve[eqn, {x, y, z}]

and now comes the answer:

Select[{x, y, z} /. sol, And @@ ( Positive /@ #) &]

Hope that helps
  Jens

David Braunholtz wrote:
> 
> WHile I've got the attention of a Mathematica expert, I am wanting to
> select a single root of a system of simultaneous equations (with
> positive values for all 3 variables) - and (being new to mathematica)
> cannot work out how to do this. I successfully get a list of roots, but
> cannot make the (you would think) easy step to reduce the list to
> only (positive) roots. Any help VERY gratefully received. I have
> searched in Mathgroup at Wolfram without finding anything.


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