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MathGroup Archive 2007

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Re: Solve[] and Eliminate[] choke on simple systems of equations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg74736] Re: Solve[] and Eliminate[] choke on simple systems of equations
  • From: dh <dh at metrohm.ch>
  • Date: Tue, 3 Apr 2007 00:25:22 -0400 (EDT)
  • References: <euqnfb$86s$1@smc.vnet.net>


Hi,

you have 17 equations and 16 variables! I think there is something fishy 

with the tripple equation:

(2*U + L)*P211 == L*P221 + U*P202 (L + 2*U)*P113 == K*P313 + K*P213 + U*P102

have fun Daniel



darrell.long at gmail.com wrote:

> Hi,

> 

> I am trying to convert some of my old stuff from another system to Mathematica.

> Below is an example of a Markov model that takes the other system a couple of

> seconds to solve, but Mathematica chews on forever (I gave up after

> about 30 minutes).

> 

> Since I'm a Mathematica newbie, perhaps there is some limitation I am

> not aware of?

> 

> eqns = {3*L*P333 == U*(P323 + P322 + P223 + P221 + P120),

> (K + 2*L + U)*P323 == 3*L*P333,

> (K + 2*U + L)*P313 == 2*L*P323,

> (2*L + U)*P322 == 2*U*P312,

> (2*U + L)*P312 == 2*L*P322 + 3*U*P302,

> 3*U*P302 == L*P312 + L*P313,

> (2*L + U)*P223 == U*(2*P213 + P212) + 2*U*P313 + U*(2*P113 + P111) +

> K*P323,

> (K + 2*U + L)*P213 == 2*L*P223,

> (2*U + L)*P212 == L*P221 + 2*U*P202,

> 3*U*P202 == L*(P213 + P212 + P211),

> (2*L + U)*P221 == U*(P212 + 2*P211),

> (2*U + L)*P211 == L*P221 + U*P202

> (L + 2*U)*P113 == K*P313 + K*P213 + U*P102,

> 3*U*P102 == L*P113 + L*P111,

> (2*U + L)*P111 == 2*U*P102 + 2*L*P120,

> (2*L + U)*P120 == U*P111,

> P333 + P323 + P313 + P322 +

>         P312 + P302 + P223 + P213 + P212 + P202 + P221 + P211 + P113 +

> P102 +

>         P111 + P120 == 1}

> vars = {P333, P323, P313, P322, P312, P302, P223, P213, P212, P202,

> P221,

>     P211, P113, P102, P111, P120}

> 

> A = Solve[eqns, vars]

> 

> 




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