## [Maxima-bugs] [ maxima-Bugs-1303241 ] solve ((2*x)/(x+5)=1/(x^2+3*x-10),x); gives wrong answer

 [Maxima-bugs] [ maxima-Bugs-1303241 ] solve ((2*x)/(x+5)=1/(x^2+3*x-10),x); gives wrong answer From: SourceForge.net - 2005-09-28 14:13:34 ```Bugs item #1303241, was opened at 2005-09-24 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*x-10),x); gives wrong answer Initial Comment: When I keyed in "solve ((2*x)/(x+5)=1/(x^2+3*x-10),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: 2005-09-28 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 cross-multiplication 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: 2005-09-24 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: (x-1)^2/(x-1)=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: 2005-09-24 11:07 Message: Logged In: YES user_id=1128112 Maxima version: 5.9.1 Maxima build date: 7:34 9/24/2004 host type: i686-pc-mingw32 lisp-implementation-type: Kyoto Common Lisp lisp-implementation-version: 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 ```

 [Maxima-bugs] [ maxima-Bugs-1303241 ] solve ((2*x)/(x+5)=1/(x^2+3*x-10),x); gives wrong answer From: SourceForge.net - 2005-09-24 14:39:54 ```Bugs item #1303241, was opened at 2005-09-24 22:39 Message generated for change (Tracker Item Submitted) made by Item Submitter 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: None Priority: 5 Submitted By: Benjamin Lau (blwy10v) Assigned to: Nobody/Anonymous (nobody) Summary: solve ((2*x)/(x+5)=1/(x^2+3*x-10),x); gives wrong answer Initial Comment: When I keyed in "solve ((2*x)/(x+5)=1/(x^2+3*x-10),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. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1303241&group_id=4933 ```
 [Maxima-bugs] [ maxima-Bugs-1303241 ] solve ((2*x)/(x+5)=1/(x^2+3*x-10),x); gives wrong answer From: SourceForge.net - 2005-09-24 15:07:54 ```Bugs item #1303241, was opened at 2005-09-24 22:39 Message generated for change (Comment added) made by blwy10v 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: None Priority: 5 Submitted By: Benjamin Lau (blwy10v) Assigned to: Nobody/Anonymous (nobody) Summary: solve ((2*x)/(x+5)=1/(x^2+3*x-10),x); gives wrong answer Initial Comment: When I keyed in "solve ((2*x)/(x+5)=1/(x^2+3*x-10),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: Benjamin Lau (blwy10v) Date: 2005-09-24 23:07 Message: Logged In: YES user_id=1128112 Maxima version: 5.9.1 Maxima build date: 7:34 9/24/2004 host type: i686-pc-mingw32 lisp-implementation-type: Kyoto Common Lisp lisp-implementation-version: 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 ```
 [Maxima-bugs] [ maxima-Bugs-1303241 ] solve ((2*x)/(x+5)=1/(x^2+3*x-10),x); gives wrong answer From: SourceForge.net - 2005-09-24 18:28:39 ```Bugs item #1303241, was opened at 2005-09-24 16:39 Message generated for change (Comment added) made by van_nek 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: None Priority: 5 Submitted By: Benjamin Lau (blwy10v) Assigned to: Nobody/Anonymous (nobody) Summary: solve ((2*x)/(x+5)=1/(x^2+3*x-10),x); gives wrong answer Initial Comment: When I keyed in "solve ((2*x)/(x+5)=1/(x^2+3*x-10),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: van_Nek (van_nek) Date: 2005-09-24 20:15 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: (x-1)^2/(x-1)=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: 2005-09-24 17:07 Message: Logged In: YES user_id=1128112 Maxima version: 5.9.1 Maxima build date: 7:34 9/24/2004 host type: i686-pc-mingw32 lisp-implementation-type: Kyoto Common Lisp lisp-implementation-version: 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 ```
 [Maxima-bugs] [ maxima-Bugs-1303241 ] solve ((2*x)/(x+5)=1/(x^2+3*x-10),x); gives wrong answer From: SourceForge.net - 2005-09-28 14:13:34 ```Bugs item #1303241, was opened at 2005-09-24 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*x-10),x); gives wrong answer Initial Comment: When I keyed in "solve ((2*x)/(x+5)=1/(x^2+3*x-10),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: 2005-09-28 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 cross-multiplication 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: 2005-09-24 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: (x-1)^2/(x-1)=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: 2005-09-24 11:07 Message: Logged In: YES user_id=1128112 Maxima version: 5.9.1 Maxima build date: 7:34 9/24/2004 host type: i686-pc-mingw32 lisp-implementation-type: Kyoto Common Lisp lisp-implementation-version: 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 ```
 [Maxima-bugs] [ maxima-Bugs-1303241 ] solve ((2*x)/(x+5)=1/(x^2+3*x-10),x); gives wrong answer From: SourceForge.net - 2006-03-26 01:48:46 ```Bugs item #1303241, was opened at 2005-09-24 08:39 Message generated for change (Comment added) made by robert_dodier 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: Closed Resolution: Invalid Priority: 5 Submitted By: Benjamin Lau (blwy10v) Assigned to: Nobody/Anonymous (nobody) Summary: solve ((2*x)/(x+5)=1/(x^2+3*x-10),x); gives wrong answer Initial Comment: When I keyed in "solve ((2*x)/(x+5)=1/(x^2+3*x-10),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: Robert Dodier (robert_dodier) Date: 2006-03-25 18:48 Message: Logged In: YES user_id=501686 Closing this report since it is already marked "invalid" and the most recent comment says the same thing. I will open a separate report about simplification x^2/x --> x . (I can't find an existing report about that.) ---------------------------------------------------------------------- Comment By: Stavros Macrakis (macrakis) Date: 2005-09-28 08:12 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 cross-multiplication 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: Volker van Nek (van_nek) Date: 2005-09-24 12:15 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: (x-1)^2/(x-1)=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: 2005-09-24 09:07 Message: Logged In: YES user_id=1128112 Maxima version: 5.9.1 Maxima build date: 7:34 9/24/2004 host type: i686-pc-mingw32 lisp-implementation-type: Kyoto Common Lisp lisp-implementation-version: 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 ```