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Math Help - Derivative of function

  1. #1
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    Post Derivative of function- tangent/normal

    y = \frac{3x+4}{x-1}

    a. Determine all values for x for which \frac{dy}{dx} exists.

    b. Find an expression for \frac{dy}{dx}.


    Here are my answers..are they correct?

    a. All real numbers not equal to 1

    b. \frac{-5}{(x-1)^2}
    Last edited by live_laugh_luv27; October 25th 2009 at 10:52 AM.
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  2. #2
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    Quote Originally Posted by live_laugh_luv27 View Post
    y = \frac{3x+4}{x-1}

    a. Determine all values for x for which \frac{dy}{dx} exists.

    b. Find an expression for \frac{dy}{dx}.


    Here are my answers..are they correct?

    a. All real numbers not equal to 1

    b. \frac{-5}{(x-1)^2}

    a) Correct.

    b) Incorrect. Should actually be -\frac{7}{(x - 1)^2}.
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  3. #3
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    Post

    ok, thanks.
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  4. #4
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    Post

    2 additional questions:

    1) Find line tangent to the curve at (8,4)

    2) Find line normal to the curve at (8,4) and determine the cooridinates of another point where this line intersects the graph.

    Here is what I came up with:

    1) y-4=-\frac{7}{64}(x-8)

    2)  y-4=\frac{64}{7}(x-8)<br />
    Is this correct? I'm unsure what the second part of the second question is asking. Any help is appreciated.
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