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MathGroup Archive 2003

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Handling expressions. Could any one find a more direct way?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg39911] Handling expressions. Could any one find a more direct way?
  • From: guillerm at aida.usal.es (Guillermo Sanchez)
  • Date: Tue, 11 Mar 2003 02:38:15 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

(*A need to obtain   {k10, k21, k12, k13, k31}  knowing that A = b
where*)

A = 0.1/(0.1 + s) + 0.2/(1 + s) + 0.7/(5 + s); 

b = (k21*k31 + k21*s + k31*s + s^2)/(k10*k21*k31 + k10*k21*s +
k13*k21*s +
     k10*k31*s + k12*k31*s + k21*k31*s + k10*s^2 + k12*s^2 + k13*s^2 +
     k21*s^2 + k31*s^2 + s^3); 

(*Here is my procedure*)

A1 = Together[ExpandAll[Factor[A]]]

n1 = Numerator[A1]

d1 = Denominator[A1]

n2 = Collect[Numerator[b], s]

d2 = Collect[Denominator[b], s]

(*Now, handing the solution for previous output -they are been
eliminated in this mail- I can obtain  {k10, k21, k12, k13, k31}*)

Solve[{k21*k31== 0.67, 2.39 == k21 + k31, k10*k21*k31 == 0.5, 
   k10*k21 + k13*k21 + k10*k31 + k12*k31 + k21*k31 == 5.6, 
   k10 + k12 + k13 + k21 + k31 == 6.1}, {k10, k21, k12, k13, k31}]
   
  (* Could any one find a more direct way?*)
  
  Guillermo Sanchez


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