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Math Help - Normal line and a parabola

  1. #1
    Member mybrohshi5's Avatar
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    Normal line and a parabola

    At what point does the normal to at intersect the parabola a second time?

    (____,_____)

    so i found the tangent line at (1,5) to be y=11x-6 so the normal line would be y=(-1/11)x-6.

    i just dont know what to do from here. i guess i dont really get what the question wants

    please help

    thank you

    chad
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  2. #2
    MHF Contributor
    skeeter's Avatar
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    Quote Originally Posted by mybrohshi5 View Post
    At what point does the normal to at intersect the parabola a second time?

    (____,_____)

    so i found the tangent line at (1,5) to be y=11x-6 so the normal line would be y=(-1/11)x-6.

    i just dont know what to do from here. i guess i dont really get what the question wants

    please help

    thank you

    chad
    when a line intersects a parabola, line = parabola
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  3. #3
    Member mybrohshi5's Avatar
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    thats what i thought too but when i graph the normal line and the parabola the normal line does not even intersect the parabola?
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  4. #4
    MHF Contributor
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    Quote Originally Posted by mybrohshi5 View Post
    thats what i thought too but when i graph the normal line and the parabola the normal line does not even intersect the parabola?
    that's because your normal line equation is incorrect.

    slope = -\frac{1}{11}

    point is (1,5)

    y - 5 = -\frac{1}{11}(x - 1)

    now change to point-slope form
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