## [Maxima-bugs] [ maxima-Bugs-996023 ] a result of a differential equation is wrong

 [Maxima-bugs] [ maxima-Bugs-996023 ] a result of a differential equation is wrong From: SourceForge.net - 2004-07-27 02:01:18 ```Bugs item #996023, was opened at 2004-07-22 11:31 Message generated for change (Settings changed) made by willisbl You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=996023&group_id=4933 Category: None Group: None >Status: Closed Resolution: None Priority: 5 Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: a result of a differential equation is wrong Initial Comment: the solution of the differential equation (1+x)*'diff(y,x)+y=1+log(1+x); is %C/(1+x)+log(1+x). The command ode2(%,y,x)returns the following solution : y=((x+1)log(x+1)+%C-1)/(x+1). It looks like there's an error of sign (with the -1 which multiplicate the constant %C) ---------------------------------------------------------------------- Comment By: Barton Willis (willisbl) Date: 2004-07-25 08:22 Message: Logged In: YES user_id=895922 This is not a bug; both solutions are correct. In Maxima's solution substitute %c --> %c + 1. This makes the two solutions identical. Since %c is an arbitrary parameter, the substitution %c --> %c + 1 is okay. Suggestion: learn how to substitute a putative solution to an equation (DE or algebraic) into the equation to check if it is correct. Barton ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=996023&group_id=4933 ```

 [Maxima-bugs] [ maxima-Bugs-996023 ] a result of a differential equation is wrong From: SourceForge.net - 2004-07-22 16:31:38 ```Bugs item #996023, was opened at 2004-07-22 09:31 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=996023&group_id=4933 Category: None Group: None Status: Open Resolution: None Priority: 5 Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: a result of a differential equation is wrong Initial Comment: the solution of the differential equation (1+x)*'diff(y,x)+y=1+log(1+x); is %C/(1+x)+log(1+x). The command ode2(%,y,x)returns the following solution : y=((x+1)log(x+1)+%C-1)/(x+1). It looks like there's an error of sign (with the -1 which multiplicate the constant %C) ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=996023&group_id=4933 ```
 [Maxima-bugs] [ maxima-Bugs-996023 ] a result of a differential equation is wrong From: SourceForge.net - 2004-07-25 13:22:20 ```Bugs item #996023, was opened at 2004-07-22 11:31 Message generated for change (Comment added) made by willisbl You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=996023&group_id=4933 Category: None Group: None Status: Open Resolution: None Priority: 5 Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: a result of a differential equation is wrong Initial Comment: the solution of the differential equation (1+x)*'diff(y,x)+y=1+log(1+x); is %C/(1+x)+log(1+x). The command ode2(%,y,x)returns the following solution : y=((x+1)log(x+1)+%C-1)/(x+1). It looks like there's an error of sign (with the -1 which multiplicate the constant %C) ---------------------------------------------------------------------- >Comment By: Barton Willis (willisbl) Date: 2004-07-25 08:22 Message: Logged In: YES user_id=895922 This is not a bug; both solutions are correct. In Maxima's solution substitute %c --> %c + 1. This makes the two solutions identical. Since %c is an arbitrary parameter, the substitution %c --> %c + 1 is okay. Suggestion: learn how to substitute a putative solution to an equation (DE or algebraic) into the equation to check if it is correct. Barton ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=996023&group_id=4933 ```
 [Maxima-bugs] [ maxima-Bugs-996023 ] a result of a differential equation is wrong From: SourceForge.net - 2004-07-27 02:01:18 ```Bugs item #996023, was opened at 2004-07-22 11:31 Message generated for change (Settings changed) made by willisbl You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=996023&group_id=4933 Category: None Group: None >Status: Closed Resolution: None Priority: 5 Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: a result of a differential equation is wrong Initial Comment: the solution of the differential equation (1+x)*'diff(y,x)+y=1+log(1+x); is %C/(1+x)+log(1+x). The command ode2(%,y,x)returns the following solution : y=((x+1)log(x+1)+%C-1)/(x+1). It looks like there's an error of sign (with the -1 which multiplicate the constant %C) ---------------------------------------------------------------------- Comment By: Barton Willis (willisbl) Date: 2004-07-25 08:22 Message: Logged In: YES user_id=895922 This is not a bug; both solutions are correct. In Maxima's solution substitute %c --> %c + 1. This makes the two solutions identical. Since %c is an arbitrary parameter, the substitution %c --> %c + 1 is okay. Suggestion: learn how to substitute a putative solution to an equation (DE or algebraic) into the equation to check if it is correct. Barton ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=996023&group_id=4933 ```