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From: songer@orchestra.ecn.purdue.edu (Christopher M Songer)
Subject: Mathematica Question
Message-ID: <1991Apr22.143807.855@noose.ecn.purdue.edu>
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Organization: Purdue University Engineering Computer Network
Distribution: usa
Date: Mon, 22 Apr 1991 14:38:07 GMT

Hi,

     This may not be precisely the place for this, but I can't find a
better so here goes: I've got a set of linear equations procduced from
nodal analysis of a fourth order filter. I'm worried about pole placement
so I need the equations solved and factored. There are six equations,
and about 18 unknowns. Eight of the unknowns are nodal voltages and six
of them should be eliminated. Yesterday I naively typed them into Mathematica
told it to solve for V1, eliminating V2 - V6 (implying that it will be interms
of Vout). Seven hours later, I stopped it. I'm running on an 040 with 12Meg 
of memory.

     What can I do to phrase the problem better so Mathematica can handle
it in a reasonable amount of time. It seemed to be adding constraining
equations to the original set. (ie, R1 != 0, R2 != 0, C1 s != 0) Can I
suppress the generation of these? Will that speed it up? Am I simply
asking too much from it?

-Chris
songer@ecn.purdue.edu