From: SourceForge.net <noreply@so...>  20050928 14:13:34

Bugs item #1303241, was opened at 20050924 10:39 Message generated for change (Comment added) made by macrakis You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1303241&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: None Group: None Status: Open >Resolution: Invalid Priority: 5 Submitted By: Benjamin Lau (blwy10v) Assigned to: Nobody/Anonymous (nobody) Summary: solve ((2*x)/(x+5)=1/(x^2+3*x10),x); gives wrong answer Initial Comment: When I keyed in "solve ((2*x)/(x+5)=1/(x^2+3*x10),x);" Maxima reports the answers as: x =  ( ( sqrt ( 6 )  2 ) / 2 ) x = ( sqrt ( 6 ) + 2 ) / 2 Where in fact, there is an additional root x = 5 I'm using the latest version of Maxima, Maxima 5.9.1 on a Windows XP SP2 Home Edition.  >Comment By: Stavros Macrakis (macrakis) Date: 20050928 10:12 Message: Logged In: YES user_id=588346 x=5 is not a root of your original equation, since your original equation is undefined at x=5. This is similar to the equation 1/x=2/x, which has no roots, although crossmultiplication gives 2*x=1*x, with solution x=0. About van Nek's example, Maxima simplifies x^2/x to x without noting that the simplification assumes that x <> 0. This is a known issue, but unfortunately not easy to deal with  how would we keep track of the context in which x<>0?  Comment By: van_Nek (van_nek) Date: 20050924 14:15 Message: Logged In: YES user_id=1269745 Hello, in this case solve gives the correct answer. Your expression is not defined for x = 5. Problematic is the following (%i5) eq: (x1)^2/(x1)=0$ (%i6) solve(eq,x); (%o6) [x = 1] My expression is not defined for x = 1. I get a solution, where there should not be a solution. Volker van Nek  Comment By: Benjamin Lau (blwy10v) Date: 20050924 11:07 Message: Logged In: YES user_id=1128112 Maxima version: 5.9.1 Maxima build date: 7:34 9/24/2004 host type: i686pcmingw32 lispimplementationtype: Kyoto Common Lisp lispimplementationversion: GCL 2.6.5 The above is the information that I just realised need to be added. Benjamin Lau [the original bug postee of this]  You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1303241&group_id=4933 