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Math Help - distance of point and line

  1. #1
    rcs
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    distance of point and line

    the distance of the line 3x - y = 6 and P (1, 2)

    my attempt : A = 3, B = - 1, C = -6,

    d = 3(1) + (-1)(2) - 6/ sq. rt. 3^2 + -1^2

    i arrived at sq. rt of 10/ 2.... is this correct? because im so confused when the book's answer is (5/2) sq. rt of 10

    i dont know which of this is correct answer. i followed the formula already but they dont have the same answer.
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    Re: distance of point and line

    I agree with your answer. \frac{\sqrt{10}}{2}
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    MHF Contributor MarkFL's Avatar
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    Re: distance of point and line

    We find:

    d=\frac{|3(1)+(-1)(2)-6|}{\sqrt{3^2+1^2}}=\frac{|-5|}{\sqrt{10}}=\frac{\sqrt{10}}{2}

    You are correct.
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  4. #4
    rcs
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    Re: distance of point and line

    why do some books in the formula of a point to a line , the denominator has negative? when will we agree to use the denominator to have negative sign... ?
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