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Math Help - Please need to finish homework

  1. #1
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    Please need to finish homework

    Need answers for 2 questions:
    1)Evaluate dy/dt for the function at the point xy^2 = 4 : dx/dt = -5, x= 4 , y = 1

    2) Find the area bounded by the given curves.
    y = x^3 , y = 4x

    THANKS
    Last edited by ArmiAldi; May 3rd 2008 at 02:18 PM.
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  2. #2
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    1. What are we supposed to do with this? Also, where does t fit in? You never specified anything about it.

    2. If you make a quick sketch of the graph, you'll see that there are two regions in which they are bounded: from -2 to 0 (where y = x^3 is bigger than y = 4x) and from 0 to 2 (where y = 4x is bigger than y = x^3).

    So, the areas bounded by both curves: A = \int_{-2}^{0} \left(x^{3} - 4x\right)dx + \int_{0}^{2} \left(4x - x^{3}\right)dx
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  3. #3
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    my mistake

    Evaluate dy/dt for the function at the point xy^2 = 4 : dx/dt = -5, x= 4, y=1
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  4. #4
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    Quote Originally Posted by ArmiAldi View Post
    Evaluate dy/dt for the function at the point xy^2 = 4 : dx/dt = -5, x= 4, y=1
    Use implicit differentiation, and then substitute. Is there a particular part of the problem that you are having trouble with?
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