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Math Help - Problem related to Population Growth

  1. #1
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    Problem related to Population Growth

    I am having a test the day right after spring break and throughout this time i don't know where to look for help, so i hope someone can help me with this problem

    Suppose that a certain population is modeled by the following Differential Equation: dP/dt = 2P(P/120-2)
    For what values of P is decreasing? For what values of P is increasing?

    I tried to solve the D.E. by setting all the P's on one side but that didnt seem to work at all
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  2. #2
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    You don't actually have to find P(t), just see where dP/dt is negative (and where positive).
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  3. #3
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    so do I just have to plug and chuck? or is there a easier way to find the exact solution?

    the solution I got is: P is descreasing when 0<P<240
    P is increasing when P>240
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  4. #4
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    Correct

    Not sure what your worry is - if you didn't do it by solving dP/dt = 0 = 2P(P/120-2) or else p^2 / 60 - 4p then try that
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