Results 1 to 2 of 2

Math Help - Solving logarithms of a difference base.

  1. #1
    Junior Member
    Joined
    Jul 2009
    Posts
    26

    Question Solving logarithms of a difference base.

    How do I solve for x of a logarithm that has two different base numbers?

    For example:

    log5 (x - 4) = log7x

    Can you show me the steps?

    Thanks.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    28
    You can use the identity log_bx = \frac{log_ax}{log_ab}

    In your case you can change log_7x to base 5 as follows

    log_7x = \frac{log_5x}{log_57}
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Comparing Two Logarithms Base 10
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: September 11th 2011, 06:59 PM
  2. difference of b to base 2010 and b to base 2009
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: December 19th 2010, 07:16 AM
  3. Please help with difference of logarithms
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: November 8th 2010, 02:25 AM
  4. Change of Base Formula Logarithms
    Posted in the Algebra Forum
    Replies: 2
    Last Post: May 2nd 2009, 08:11 PM
  5. Difference between base and ordered base
    Posted in the Advanced Algebra Forum
    Replies: 4
    Last Post: February 18th 2009, 05:59 PM

Search Tags


/mathhelpforum @mathhelpforum