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Solve[] for equations?

  • To: mathgroup at
  • Subject: [mg31928] Solve[] for equations?
  • From: "Doug VanGoethem" <djvango at>
  • Date: Wed, 12 Dec 2001 04:14:14 -0500 (EST)
  • Organization: Sandia National Laboratories, Albuquerque, NM USA
  • Sender: owner-wri-mathgroup at

I have a system of equations

eq1 = Rac == R1(R2+R3+R4)/(R1+R2+R3+R4)
eq2 = Rad == R2(R1+R3+R4)/(R1+R2+R3+R4)
eq3 = Rbc == R3(R1+R2+R4)/(R1+R2+R3+R4)
eq4 = Rbd == R4(R1+R2+R3)/(R1+R2+R3+R4)

I'd like to get R1, R2, R3, and R4 in terms of Rac, Rad, Rbc, and Rbd.  Four
equations, four unknowns -- it seems simple in concept so I figured Mathematica
could do it easily.  I thought that something along the lines of:

Solve[{eqs},{R1, R2, R3, R4}] or
Solve[{eqs}, R1, {R2, R3, R4}]

would have worked, but these give {}.  They only permutation of commands
that seemed to do anything was something like

Solve[eq1, R1]

but one can do that easily by hand so what's the point.

Is there some other command I should be using besides Solve?   Is there some
mathematical reason that I don't recognize as to why this won't work?   I
would appreciate any insights.

Thanks in advance,
Doug VanGoethem

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