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Finding a function

  1. Apr 13, 2009 #1
    write a function that starts at 20 and triples every 7
     
  2. jcsd
  3. Apr 13, 2009 #2

    arildno

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    I'm sure you have just learnt about exponential functions!

    Utilize that knowledge to find a solution to your problem.
     
  4. Apr 13, 2009 #3
    Hello jared89, welcome to the forum

    You could use the exponential function in a general form and start fitting it to the two conditions you have, however there is a slightly more advanced way. Write out the two conditions as:

    [tex]f(0)=20[/tex]
    [tex]f(7x)=2f(x)[/tex]

    Take the derivative of the second one and use in it the original again. You will end up with a first order differential equation giving as solution the exponential function. Using the first equation as boundary gives then the function you are looking for.

    Can you do this?
     
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