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!

Homework Help: Exponential equation

  1. Jul 5, 2010 #1


    User Avatar

    1. The problem statement, all variables and given/known data

    Solve for x:


    2. Relevant equations

    It becomes 4x=11

    3. The attempt at a solution

    I have no idea where to go from here. We never had a problem with such an immovable number such as 11 to work with. Calculators are not allowed to be used either.
  2. jcsd
  3. Jul 5, 2010 #2
    Use the definition of a logarithm.
  4. Jul 5, 2010 #3


    User Avatar

    Okay, I think I'm on the right track but I'm still not sure where to go with this:

    4log411= ?
  5. Jul 5, 2010 #4
    For logarithms it is always true that:

    a^{x} = b \Leftrightarrow x = \log_{a}{b}, \; a, b > 0, \; a \neq 1

    From here we have the fundmanetal property of logarithms:

    a^{\log_{a} b} = b
  6. Jul 5, 2010 #5


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Take the log of both sides to any base and solve for x. It doesn't have to be base 4 and if you were after a decimal approximation you would likely want to use base e or base 10.
  7. Jul 6, 2010 #6


    User Avatar

    Okay, so I attempted a change of base and got this:

    ln11/ln4 ~ 1.729

    Is this how it eventually would end up?

    Thanks for all your help! Logarithms are just driving me nuts for some reason
  8. Jul 6, 2010 #7
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook