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Math Help - Equation of a Tangent Line

  1. #1
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    Equation of a Tangent Line

    How do I find the equation of the tangent line to the graph of f(x)=(x^2+n)(x-n) at a given point (-x,-y)
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  2. #2
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    I'm not sure if i'm right, but

    expand:

    (x^2+n)(x-n)

    =x^3-x^2*n+nx-n^2

    take the first derivative

    so f'(x)=3x^2-2xn+n

    -f'(x)=3x^2-2xn+n
    m=-(3*(-x)^2-2*-x*n+n)
    m=-3x^2-2xn-n


    so the tangent line is

    y=mx+b
    y=(-3x^2-2xn-n)*x+b

    b depends on your n, i don't feel like working it out though sorry




    I think that's right but i've never done a problem like this so...
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