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Math Help - Figuring out X on a parallel line without graphing

  1. #1
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    Figuring out X on a parallel line without graphing

    Hello, i'm stuck on this question:

    Determine the value of x so that the line segment with endpoints A(x,3) and B(1,7) is parallel to the line segment with endpoints C(2,-4) and D(5,-2)

    Ok, i got the slope by using the forumla Y2 -Y1 over X2 - X1

    -4 -(-2)
    ---------
    2 -5
    =
    -2
    -----
    -3

    That is the slope, now everytime i get to this point, i have no choice but to multiply, so in this case X = -5, so coordinates would be (-5, 3). But this answer was found through graphing. On a test, i won't have the time to graph, so how can i find x without having to graph it (when i have the slope already).
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
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    New York, USA
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    Quote Originally Posted by simplekin View Post
    Hello, i'm stuck on this question:

    Determine the value of x so that the line segment with endpoints A(x,3) and B(1,7) is parallel to the line segment with endpoints C(2,-4) and D(5,-2)

    Ok, i got the slope by using the forumla Y2 -Y1 over X2 - X1

    -4 -(-2)
    ---------
    2 -5
    =
    -2
    -----
    -3

    That is the slope, now everytime i get to this point, i have no choice but to multiply, so in this case X = -5, so coordinates would be (-5, 3). But this answer was found through graphing. On a test, i won't have the time to graph, so how can i find x without having to graph it (when i have the slope already).
    to be parallel means they have the same slope, so using the \frac {y_2 - y_1}{x_2 - x_1} formula, we want:

    \frac {7 - 3}{1 - x} = \frac {-2 - (-4)}{5 - 2}

    now solve for x
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