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Math Help - first derivative test

  1. #1
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    first derivative test

    Hi Everyone,

    I'm new in the forum.

    I would like to know if my exercise is correct, often I make mistake in the calculation. If there is a way I can check my work.

    Here is the question:


    *Using the strategy to apply the First Derivative Test, classify the
    left-hand stationary point:
    stationary points:
    X= -3 and x= 1
    .*


    Step 1: the left stationery point of f is at x= -3;

    Step 2: To classify the stationery point at x= -3, we choose test points xl= -4 and xr= -2, say. Then we have
    f (xl)= f (-4) = 3(-4)(-1)(-5) = -60 < 0
    f (xr)= f (-2) = 3(-2)(1)(-3) = 18 > 0


    so f has a local minimum at x = -2, by the first derivative test.



    I hope there is no mistake in that
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  2. #2
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    Quote Originally Posted by valerie-petit View Post
    Hi Everyone,

    I'm new in the forum.

    I would like to know if my exercise is correct, often I make mistake in the calculation. If there is a way I can check my work.

    Here is the question:


    *Using the strategy to apply the First Derivative Test, classify the
    left-hand stationary point:
    stationary points:
    X= -3 and x= 1
    .*


    Step 1: the left stationery point of f is at x= -3;

    Step 2: To classify the stationery point at x= -3, we choose test points xl= -4 and xr= -2, say. Then we have
    f (xl)= f (-4) = 3(-4)(-1)(-5) = -60 < 0
    f (xr)= f (-2) = 3(-2)(1)(-3) = 18 > 0


    so f has a local minimum at x = -2, by the first derivative test. Mr F says: Should that be x = -3 .....? Otherwise it all looks OK. Keeping in mind of course that you have not given the rule for the function so the values themselves can't actually be checked ......



    I hope there is no mistake in that
    ..
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