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Math Help - Logs solving for x

  1. #1
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    Logs solving for x

    Solving for x:

    log4 (x - 10) + log4 (x + 10) = 4
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  2. #2
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    e^(i*pi)'s Avatar
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    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
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