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MathGroup Archive 2006

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Re: Setting up equations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg66038] Re: Setting up equations
  • From: dh <dh at metrohm.ch>
  • Date: Thu, 27 Apr 2006 04:36:29 -0400 (EDT)
  • References: <e2nd3i$33m$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com


Hi Yaroslav,

you could transform your expression into the null polynomial and extract 

coefficents of x,y,z. E.g.:

eq1=5 x + 6 y + 7 z == a x + b y + c z

eq2= Subtract @@ eq1

Extracting coefficients:

cof= Coefficient[eq2,{x,y,z}]

and putting them into an new equation:

(# == 0) & /@ cof

this yields a list of equation that you may solve by Solve or Reduce



Daniel



Yaroslav Bulatov wrote:

> I'm trying to do things of the form

> Solve[5 x + 6 y + 7 z == a x + b y + c z, {a, b, c}]

> 

> But since x,y,z are variables, what I really mean is

> Solve[5==a && 6==b && 7==c], so I need to convert to this form

> 

> If I only have one variable, the following does what I need

> 

> LogicalExpand[a*x + b*x^2 + O[x]^3 == 2*x + 3*x^2 + O[x]^3]

> 

> But what to do if I have several variables?

> 



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