Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Ln(x) =f(x)

  1. Jul 7, 2010 #1
    Just came across this for a program I'm writing. I need to be able to solve an equation of the form ln(x) =f(x) where f isn't a logarithm. specifically, it's ln(x)=-x^2+ a*x+b.

    Is this solvable for x or do I need a numeric approximation?
  2. jcsd
  3. Jul 7, 2010 #2
    Re: ln(x)=f(x)


    You must use a numerical approximation to solve this equation.

  4. Jul 7, 2010 #3


    User Avatar
    Science Advisor
    Homework Helper

    Re: ln(x)=f(x)

    It may be possible with the W-function, but I'd suggest numerical methods (Brent's method or the cosecant method).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook