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: Logarithm Proof

  1. Dec 1, 2008 #1
    1. The problem statement, all variables and given/known data


    1/log3a + 1/log4a = 1/log12a

    2. Relevant equations

    Logarithms rules (addition, subtraction, power, etc.)


    3. The attempt at a solution

    Left Side:

    1/log3a + 1/log4a
    =log3a+log4a/log12a (via common denominator)

    The problem is how to add logarithms with different bases. I tried converting the log3a to log4a (I get log4a/log43). After that, I subbed it back into the equation.


    But I don't think that gets me anywhere...

    Right side still remains the same (1/log12a)

    Any help is appreciated! Thanks in advance :).

    P.S. What program do people use to make their equations look so neat (the fraction looks real - ex. 1/4 really looks like 1 (horizontal line) 4)?
  2. jcsd
  3. Dec 1, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    Let's just convert everything to a single log base, like log_12. E.g. log_3(a)=log_12(a)/log_12(3).
  4. Dec 1, 2008 #3
    Oh, wow. Sigh, I hate it when you take the wrong approach in proving Left Side equals Right Side.

    Thanks for the help! Can't believe it was so simple after your suggestion :).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook