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Math Help - Would like someone to check my answer for finding gradients and perpendicularity

  1. #1
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    Would like someone to check my answer for finding gradients and perpendicularity

    Points P ≡ (-1,1), Q ≡ (1,-4), R ≡ (6,-2) are given. Find the gradients of the lines PQ and QR, and show that they are perpendicular.

    Here's what I've got - is this correct?

    slope of PQ = (y2 - y1) /(x2 -x1) = (-4 -1)/(1 - (-1)) = -5/2

    slope of QR = ( -2 - (-4) ) / (6 - 1) = 2/5

    slope of PQ * slope of Qr = -5/2 * 2/5 = -1

    so PQ perpendicular to QR
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  2. #2
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    Quote Originally Posted by brumby_3 View Post
    Points P ≡ (-1,1), Q ≡ (1,-4), R ≡ (6,-2) are given. Find the gradients of the lines PQ and QR, and show that they are perpendicular.

    Here's what I've got - is this correct?

    slope of PQ = (y2 - y1) /(x2 -x1) = (-4 -1)/(1 - (-1)) = -5/2

    slope of QR = ( -2 - (-4) ) / (6 - 1) = 2/5

    slope of PQ * slope of Qr = -5/2 * 2/5 = -1

    so PQ perpendicular to QR
    Looks good to me.

    -Dan
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