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Math Help - Need help!! logarithms and exp.func thx!

  1. #1
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    Need help!! logarithms and exp.func thx!

    I have an equation of

    N(t)= 3000e^(kt) - 4500 (t-3)

    Set N(t)=0, how can i find t value???

    and k is given: k=(1/3)* ln(3)


    Can u explain me with simple rules...and answer

    Thank you
    Last edited by mookie; May 24th 2009 at 11:04 AM.
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  2. #2
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    Quote Originally Posted by mookie View Post
    I have an equation of

    N(t)= 3000e^(kt) - 4500 (t-3)

    Set N(t)=0, how can i find t value???

    and k is given: k=(1/3)* ln(3)


    Can u explain me with simple rules...and answer

    Thank you
    go back to your previous thread.

    http://www.mathhelpforum.com/math-he...-cake-4-u.html
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  3. #3
    MHF Contributor Amer's Avatar
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    there is a property for log or Ln said

    log y^2 = 2 log y & log e^y = y & e^log(y) = y


    so
    k = 1/3 ln(3) = ln( 3^(1/3))

    N(t)= 3000e^(kt) - 4500 (t-3)

    3000e^(kt) = 4500 (t-3)
    3000e^(t ln( 3^(1/3)) = 4500 (t-3)
    3000e^( ln(3^(t/3)) = 4500 (t-3)
    30(3^(t/3)) = 45 (t-3)
    6 3^(t/3) = 3^2 (t-3)

    I think there is a mistake in this question
    t/3 = 2 ...... t=6
    6 = t-3 ......t=9
    I think 1500 should be instead of 3000
    or 13500 instead of 4500

    I think
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