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Math Help - The Straight Line

  1. #1
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    The Straight Line

    Three lines have the equations 2x+3y-4=0
    3x-y-17=0
    x-3y-10=0

    Show wether these lines are cocurrent or not.

    Anyone know how to do this, darn im rubbish at maths
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  2. #2
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    Hello, mattymaths!

    Given three lines: . \begin{array}{cccc}2x+3y-4&=&0 &{\color{blue}[1]}\\ 3x-y-17&=&0 & {\color{blue}[2]}\\ x-3y-10&=&0 &{\color{blue}[3]}\end{array}

    Show whether these lines are concurrent or not.

    "Concurrent" means they intersect at one point.

    Find the intersection of [1] and [3].
    Find the intersection of [2] and [3].

    Are they the same point?

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  3. #3
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    Thanks for the reply!

    Would i be right then rearranging the equations [1] and [2] so they look like
    2x+3y=4
    3x-y=17

    and then solving simultaneously?
    Then doing the same for [2] and [3]?
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  4. #4
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    Yes . . . absolutely right!

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  5. #5
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    I thought that, but i just cant seem to get it right, can you see where im going wrong?

    [1] 2x + 3y = 4
    [2] 3x -y = 17 X3

    [1] 2x + 3y=4
    [2] 9x - 3y=51

    11x=55?

    doesnt seem to work out right, i'm not too sure what ive done wrong

    SORRY I'VE NOTICED MY INCREDIBLY SILLY MISTAKE!

    Anyway i done 2(5)+3y=4
    so 10+3y=4
    3y=4-10
    3y=-6
    y=-2

    so (5,-2) is this right? i hope so ha!

    Thank you very much for the replies btw
    Last edited by mattymaths; August 31st 2008 at 10:32 AM. Reason: Simple mathematical error ha
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