maxima-bugs

 [Maxima-bugs] [ maxima-Bugs-1708293 ] Spurious solutions (zero denominators) returned by solve From: SourceForge.net - 2007-06-29 23:36:38 ```Bugs item #1708293, was opened at 2007-04-26 12:13 Message generated for change (Comment added) made by robert_dodier You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1708293&group_id=4933 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Lisp Core - Solving equations Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) >Summary: Spurious solutions (zero denominators) returned by solve Initial Comment: I was trying to calculate the equation of a hyperbola of the type x^2/a^2 - y^2/b^2 = 1, given two points. Maxima finds, among others, also a wrong solution [a=0,b=0]. (%i4) hyp:x^2/a^2-y^2/b^2=1\$ (%i4) eq1:hyp,x=-5/2,y=-3/4\$ (%i4) eq2:hyp,x=10/3,y=4/3\$ (%i4) solve([eq1,eq2],[a,b]); (%o4) [[a=2,b=-1],[a=-2,b=-1],[a=2,b=1],[a=-2,b=1],[a=0,b=0]] F. Buratti (Italy) bufranz@... Maxima version: 5.11.99rc2 Maxima build date: 20:46 4/19/2007 host type: i686-pc-mingw32 lisp-implementation-type: GNU Common Lisp (GCL) lisp-implementation-version: GCL 2.6.8 ---------------------------------------------------------------------- >Comment By: Robert Dodier (robert_dodier) Date: 2007-06-29 17:36 Message: Logged In: YES user_id=501686 Originator: NO Merging bug report # 1700056 (same problem); I'll mark 1700056 as a dup. Also revise summary to make it more descriptive. ------------- begin 1700056 ------------- With Maxima 5.11.0, Using Lisp CLISP 2.41 (2006-10-13) q1 : 2/x + 5/y = -19/15; q2 : 1/y -5/x = -4/3; sys :[q1,q2]; var : [x,y]; solve(sys,var); /*==> [[x = 5,y = -3],[x = 0,y = 0]] This seems to happen only with systems. I was not able to reproduce this bug with a single equation and a single variable. -------------- end 1700056 -------------- ---------------------------------------------------------------------- Comment By: Stavros Macrakis (macrakis) Date: 2007-05-01 12:57 Message: Logged In: YES user_id=588346 Originator: NO Yes, this is a bug. Here is a simpler example: solve([1/a-1/b=1,a=b],[a,b]) => [[a=0,b=0]] ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1708293&group_id=4933 ```