1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Is this imposible?

  1. Sep 24, 2010 #1
    Find the solutions of 5^x=2x+1 by ordinary methods? if it can´t be found by these ways, then prove that it's imposible.
  2. jcsd
  3. Sep 24, 2010 #2
    It depends on what you mean by ordinary methods.

    By inspection, x=0.
  4. Sep 24, 2010 #3
    but, there is other answer, how you find it?
  5. Sep 25, 2010 #4


    User Avatar
    Gold Member

    The exponent ^5 is behind the X or after?
  6. Sep 25, 2010 #5
    Ordinary method consists in studying the function y=(5^x)-(2x+1)
    This shows that two roots exist (one of them is obvious).
    Drawing the graph of the function allows to obtain a first approximate of the second root.
    Then, numerical computation leads to the value of the root, as accurate as we want. There are a lot of numerical methods : Newton-Raphson and many other...
    Analytical solving is outside the scope of ordinary methods. It requires the use of a special function : the Lambert W function.

    Attached Files:

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook