[Maxima-bugs] [ maxima-Bugs-932395 ] solve confused by ratvars

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Bugs item #932395, was opened at 2004-04-09 11:17
Message generated for change (Settings changed) made by robert_dodier
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>Category: Lisp Core - Solving equations
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Stavros Macrakis (macrakis)
Assigned to: Nobody/Anonymous (nobody)
Summary: solve confused by ratvars

Initial Comment:
  solve(rat(a+c,a,b,c,d),[a,b])
    => [[a=-%r1, b=%r1]]    NO!

Remove the extra variable:

  solve(rat(a+c,a,b,c),[a,b])
     => [[a = - c, b = %r2]]     OK

Also works fine if you call algsys directly:

  algsys([rat(a+c,a,b,c,d)],[a,b]);

At first I thought this had something to do with the 
variable *ordering* in the first case, but in fact it 
happens with all orderings.  The problem is the number 
of ratvars.

Note that this is *not* an artificial situation.  It is 
common to have CREs with more ratvars than they use 
after arithmetic operations, e.g. rat(a+b)-rat(a).


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