Results 1 to 2 of 2

Thread: Logs solving for x

  1. March 23rd 2009, 04:02 PM #1
    tmac11522
    tmac11522 is offline
    Junior Member
    Joined
    Jan 2009
    Posts
    40

    Logs solving for x

    Solving for x:

    log4 (x - 10) + log4 (x + 10) = 4
    Follow Math Help Forum on Facebook and Google+
  2. March 23rd 2009, 04:11 PM #2
    e^(i*pi)
    e^(i*pi) is offline
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by tmac11522 View Post
    Solving for x:

    log4 (x - 10) + log4 (x + 10) = 4
    log_a(m) + log_a(n) = log_a{(mn)}

    in your case

    log_4{((x+10)(x-10))} = 4

    log_4{(x^2-100)} = 4

    x^2-100=4^4

    x^2-356=0

    x = 2\sqrt{89}
    Last edited by e^(i*pi); March 23rd 2009 at 04:21 PM. Reason: oops 4^4 = 256 not 16
    Follow Math Help Forum on Facebook and Google+
« Two problems.... | Polynomial Help »

Similar Math Help Forum Discussions

  1. Solving for x with logs
    Posted in the Pre-Calculus Forum
    Replies: 6
    Last Post: November 29th 2011, 03:12 PM
  2. [SOLVED] solving for X with logs
    Posted in the Pre-Calculus Forum
    Replies: 10
    Last Post: May 20th 2011, 08:57 AM
  3. Solving with logs
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: November 10th 2009, 09:49 PM
  4. Solving Logs
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: September 19th 2009, 03:42 PM
  5. solving for x using logs
    Posted in the Algebra Forum
    Replies: 5
    Last Post: September 11th 2009, 04:11 PM

Search Tags


/mathhelpforum @mathhelpforum