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Math Help - tangents

  1. #1
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    tangents

    find an equation of the line tangent to f(x)=x^2-4x at P(3,-3)
    thank you
    Last edited by mxhockey140; December 15th 2008 at 09:29 AM.
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  2. #2
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    Quote Originally Posted by mxhockey140 View Post
    find an equation of the line tangent to f(x)=x^2-4x at P(3,-3)
    thank you
    Hi mxhockey,

    The tangent line you are looking for has the form y=mx+b where m is the same as the gradient of your function f(x) at (3, -3). So just find f'(x) and plug in x = 3 to find m.
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  3. #3
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    Well, we seek a line crossing a given point. And tangent means "toucher" that means the slope tangent = local slope of the curve at the given point.
    in the end we can calculate the local slope with usage of derivation.
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