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Math Help - equation of a line

  1. #1
    Senior Member euclid2's Avatar
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    equation of a line

    given the vertices p(3,7), Q(-8,2) R(-4,-9) Determine the equation of the altitude that passes through the point P.

    Thanks
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  2. #2
    Senior Member nikhil's Avatar
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    Lightbulb Here it is

    The altitude through P is perpendicular to QR.
    So if slope of QR =m then slope of altitude will be -1/m
    so equation of altitude will be
    y-7=(-1/m)(x-3)
    hope you can calculate m.if not then you may ask.
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  3. #3
    Senior Member euclid2's Avatar
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    I found the slope of the line passing through p to be 4/11
    y2-y1/x2-x1
    -9-2/-4--8
    m=-11/4
    Then negative reciprocal so its 4/11
    Then i plug it into y=mx+b
    and get
    4=4/11(3)+b
    I can't see to figure it out from here
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  4. #4
    Senior Member nikhil's Avatar
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    Quote Originally Posted by euclid2 View Post
    I found the slope of the line passing through p to be 4/11
    y2-y1/x2-x1
    -9-2/-4--8
    m=-11/4
    Then negative reciprocal so its 4/11
    Then i plug it into y=mx+b
    and get
    4=4/11(3)+b
    I can't see to figure it out from here
    it should not be 4=4/11(3)+b
    it should be
    7=(4/11)(3)+b
    11b=65
    b==65/11
    so equation will be
    y=(4/11)x+65/11
    hope this helps.
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