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Math Help - Weird equation help

  1. #1
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    Weird equation help

    Suppose that for some values of A and r, P(t) = Ae^(rt) and we know that P(5)=200 and P(7)=325. Find A and r.

    I can't do it, because I cannot isolate A, or r to solve for them.
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  2. #2
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    Quote Originally Posted by Velvet Love View Post
    Suppose that for some values of A and r, P(t) = Ae^(rt) and we know that P(5)=200 and P(7)=325. Find A and r.

    I can't do it, because I cannot isolate A, or r to solve for them.
    Ae^5r = 200 implies A = 200/e^5r
    so 325 = Ae^7r = 200e^7r/e^5r = 200e^2r
    so r = .5*ln(325/200), and we can plug this in to find A
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