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Thread: Points and lines

  1. #1
    Junior Member
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    May 2008
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    Points and lines

    Hello,

    Is there a simpler way of locating whether any of the points (-3,-2), (-1,-2), (1,-2), (3,-2) are below both these lines?

    2x-y=4 and x+2y=-3

    I'm just substituting each and every x value of the points in and seeing whether the answer's y value is below the equation's y value.

    Is there a simpler way than substitution or graphing (I can't use graphs here)?
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  2. #2
    Super Member
    Joined
    Jan 2009
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    Quote Originally Posted by Kataangel View Post
    Hello,

    Is there a simpler way of locating whether any of the points (-3,-2), (-1,-2), (1,-2), (3,-2) are below both these lines?

    2x-y=4 and x+2y=-3

    I'm just substituting each and every x value of the points in and seeing whether the answer's y value is below the equation's y value.

    Is there a simpler way than substitution or graphing (I can't use graphs here)?
    Depends on the definition of "simpler".
    Using vectors is a rather simple way to answer it.

    However, from the phrasing of the question and the data given, the "plug & check" is about as simple as one can get.


    "below" means "less than" in your context.

    The first item I would do is re-write the equations and isolate y.

    Your method is good.
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