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#1905 Solving equations with logarithms

closed
nobody
5
2010-03-23
2010-02-16
traxi
No

(%i1) solve([log(x)*x=0], [x]);
(%o1) [x=1,x=0]

Should only be [x=1,x=0]

Discussion

  • traxi

    traxi - 2010-02-17

    Should only be x=1

     
  • traxi

    traxi - 2010-02-17
    • summary: Solving equations with logarthims --> Solving equations with logarithms
     
  • Barton Willis

    Barton Willis - 2010-02-18

    The alternative solver (to_poly_solve) can not solve this equation either:

    (%i13) load(to_poly_solver)$
    (%i12) %solve([log(x)*x=0], [x]);
    Division by 0
    (%o12) %union()

    Thanks for this report--I'll try to fix to_poly_solve function.

     
  • Stavros Macrakis

    I think you mean "should only be [x=1]".

    Maxima actually got lucky here, because x=0 is arguably a solution by continuity, since limit(log(x)*x,x,0) = 0 (even for negative x).

     
  • traxi

    traxi - 2010-02-19

    I'm only interested in real results.
    Is it possible to configure maxima, ony to get real results in this case?

     
  • Nobody/Anonymous

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  • Dieter Kaiser

    Dieter Kaiser - 2010-03-08

    As mentioned in a posting below, the solution x=0 might be considered as a solution too.
    Setting the resolution to Wont Fix and the status to pending.
    Dieter Kaiser

     
  • Dieter Kaiser

    Dieter Kaiser - 2010-03-08
    • status: open --> pending
     
  • SourceForge Robot

    This Tracker item was closed automatically by the system. It was
    previously set to a Pending status, and the original submitter
    did not respond within 14 days (the time period specified by
    the administrator of this Tracker).

     
  • SourceForge Robot

    • status: pending --> closed
     

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