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Re: NSolve problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg59657] Re: NSolve problem
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Tue, 16 Aug 2005 04:39:46 -0400 (EDT)
  • Organization: The University of Western Australia
  • References: <dcsc67$q0k$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

In article <dcsc67$q0k$1 at smc.vnet.net>,
 Enrique Zeleny <ezeleny at fcfm.buap.mx> wrote:

> I f I try to solve these equations
> 
> Solve[{2 x + 3 y == 8 + I 7,
>     3 x +  y == 5 + 7 I, -2 I x + (1 + 3 I) y == 3 + 5 I}]
> 
> the result is
> 
> {{x -> 1 + 2*I, y -> 2 + I}}
> 
> but if I have
> 
> Solve[{2 x + 3 y == 8 + I 7,
>     3 x +  y == 4.99999999999999 + 7 I, -2 I x + (1 + 3 I) y == 3 + 5 I}]

Others have explained the answer returned by Mathematica. Here is 
another approach, suitable since you have linear equations.

[1] Load the LinearAlgebra stubs:

  << LinearAlgebra`

[2] Determine the matrix A, and right-hand side b:

  {A, b} = LinearEquationsToMatrices[
    {2*x + 3*y == 8 + I*7,     
     3*x + y == 4.99999999999999 + 7*I,     
     (1 + 3*I)*y - 2*I*x == 3 + 5*I}, {x, y}]

[3] Solve using LinearSolve:

  LinearSolve[A,b]

Cheers,
Paul

-- 
Paul Abbott                                      Phone: +61 8 6488 2734
School of Physics, M013                            Fax: +61 8 6488 1014
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        http://InternationalMathematicaSymposium.org/IMS2005/


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