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Help: logarithmic equation

  1. Sep 21, 2004 #1
    Hi everyone. I'm new in the forum and I'd need an help to solve this equation (sorry, I think it's quite easy but I'm not an expert of mathematics..):

    a*x + b*ln(x) = c

    where a, b, c are parameters and I need to find the value of x.

    Do I need to use techniques of differential equations?

    Thanks a lot for any help.
  2. jcsd
  3. Sep 21, 2004 #2
    You need to use Numerical Techniques.
    Have u come across Newton Raphson method ? It should do just fine on this one.

    -- AI
  4. Sep 21, 2004 #3
    No, I've never used the Newton Raphson method.. thanks, i'll have a look to this technique, however, I suppose I need to use some maths softwares to compute the result, isn't it?
  5. Sep 21, 2004 #4


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    No. Any scientific calculator will work. You could also use Excel, if you choose.

    Hopefully, you won't have to go through too many iterations.
  6. Sep 21, 2004 #5


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    There is also the "Lambert's W" function. It is defined specifically as "W(x) is the y satisfying yey= x". In other words, it is the inverse of the function xex.
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