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Math Help - related rates

  1. #1
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    related rates

    if xy^2=12 and dy/dx=6, find dx/dy when y=2
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  2. #2
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    If we differentiate y^{2}=\frac{12}{x} we get, 2y\frac{dy}{dx}=\frac{-12}{x^{2}}.

    Can you substitute values in to get our answer?
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  3. #3
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    Quote Originally Posted by ANDS! View Post
    If we differentiate y^{2}=\frac{12}{x} we get, 2y\frac{dy}{dx}=\frac{-12}{x^{2}}.

    Can you substitute values in to get our answer?

    so would it look like this:

    6=-12/4x^2?
    if i solve for x... i dont get the same answer as they have in the text book
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  4. #4
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    I didn't see that first line: They want you to differenciate Y with respect to X, and X with respect to Y? o_0 Have you written the problem correctly? I am referring to this part here:

    dy/dx=6, find dx/dy
    What is the answer they give you in the book?
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  5. #5
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    Quote Originally Posted by ANDS! View Post
    I didn't see that first line: They want you to differenciate Y with respect to X, and X with respect to Y? o_0 Have you written the problem correctly? I am referring to this part here:



    What is the answer they give you in the book?

    yes, the question is correct.. the one above
    if xy^2=12 and dy/dx=6, find dx/dy when y=2
    the answer they have is -18
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