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Math Help - Natural logarithms

  1. #1
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    Question Natural logarithms

    Write this expression using only natural logarithms:

    log (x-y) ----> (1/5 is the base)
    1/5


    Thanks for any help!
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  2. #2
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    Quote Originally Posted by live_laugh_luv27 View Post
    Write this expression using only natural logarithms:

    log (x-y) ----> (1/5 is the base)
    1/5


    Thanks for any help!
    use the change of base formula ...

    \log_b{a} = \frac{\ln{a}}{\ln{b}}
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  3. #3
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    ok , and i got ln(x-y) / ln(1/5). Would I leave this as the answer, or would I distribute to get lnx - lny / ln1 - ln5 ??
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  4. #4
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    review your log properties ...

    first off, \ln(x-y) \neq \ln{x} - \ln{y} ,and

    \ln\left(\frac{1}{5}\right) = \ln{1} - \ln{5} = 0 - \ln{5} = -\ln{5}
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  5. #5
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    so, ln(x-y) can't be reduced?
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  6. #6
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    no ... you're stuck with it.
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  7. #7
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    ok thanks for the help
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