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Math Help - differentation question

  1. #1
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    differentation question

    Hi everyone i was just wondering if anyone could help with this differentiation question it is :

    Use differentitation to find the coordinates of the stationary points on the curve.
    Y= x + 4/x
    And determine whether each stationary point is a maximum point or minimum point.
    Find the set of values of x for which y increase as x increases.

    Thanks Gracey

    Even if you can help with a small part of the question i would be grateful
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  2. #2
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    I think this is what you mean:

    y=x+\dfrac{4}{x}
    \dfrac{dy}{dx}=1-\dfrac{4}{x^2}
    0=1-\dfrac{4}{x^2}
    x=\pm2

    Look at the sign of the derviative in the interval (-\infty, \infty)

    you will find that it is a local max at x=-2 and local min at x=2

    Therefore the function is increasing from (-\infty,-2) and (2,\infty) and decreasing on (-2,0), (0,2)
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  3. #3
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    thankyou so much that is excellent.
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