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MathGroup Archive 2006

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Re: Beginner--How to resolve a simple system of equation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg69016] Re: Beginner--How to resolve a simple system of equation
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Sat, 26 Aug 2006 04:40:06 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <ecoqlu$3ai$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

abdou.oumaima at hotmail.com wrote:
> Hello Math groupe
> 
> I'm in front of one system of equations but inable to find the result:
> 
> G= {{0.1875 + 0.2673054 ksi, -0.12500 - 0.1666667 ksi}, {0.12500 + 0.1666667 ksi, -0.0833333 - 0.131278 ksi}}
> 
> F= {{0.1875 + 0.01730547 ksi, 0.12500}, {0.12500, 0.0833333 - 0.0062781468 ksi}}
> 
> IN={1,0}
> 
> I have: G OUT = F IN
> 
> I have to find OUT independent of ksi. (LinearSolve doesn't give me the result, perhaps I didn't use the right syntax)
> 
> Any suggestions will be very welcome.
> Best regards.
> Lian!

Hi Lian,

Have you tried Solve with the last argument set to ksi (the last 
argument of Solve is for variable elimination)? Also, have you written 
your product as dot product and not as regular multiplication? I hope 
the following helps,

G = {{0.1875 + 0.2673054*ksi, -0.125 -
  0.1666667*ksi}, {0.125 + 0.1666667*ksi,
  -0.0833333 - 0.131278*ksi}};
F = {{0.1875 + 0.01730547*ksi, 0.125},
  {0.125, 0.0833333 - 0.0062781468*ksi}};
IN = {1, 0};
OUT = {x, y};
Solve[G . OUT == F . IN, {x, y}, ksi]

--> {{x -> 2.3114239238154674*^-13*(4.3263525*^12 - 
5.223408591661797*^12*Sqrt[-7.2484628939677336*^-6 + 
y]*Sqrt[-1.1376936309361483*^-6 + y] - 2.33918391018*^12*y)}, {x -> 
2.3114239238154674*^-13*(4.3263525*^12 + 
5.223408591661797*^12*Sqrt[-7.2484628939677336*^-6 + 
y]*Sqrt[-1.1376936309361483*^-6 + y] - 2.33918391018*^12*y)}}

Best regards,
Jean-Marc


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