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Math Help - Finding a linear equation which passes through points

  1. #1
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    Finding a linear equation which passes through points

    Ok, Im not quite sure what to do here, could anyone help please?

    i have 4 questions

    1) (7,0) (0,2)

    2) (2,4) (-3,1)

    3) (-3,2) (6,8)

    4) (4,3) (8, 12)

    help would be much appreciated

    thank you all
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  2. #2
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    Quote Originally Posted by damonneedshelp View Post
    Ok, Im not quite sure what to do here, could anyone help please?

    i have 4 questions

    1) (7,0) (0,2)

    2) (2,4) (-3,1)

    3) (-3,2) (6,8)

    4) (4,3) (8, 12)

    help would be much appreciated

    thank you all
    I will do 2) for you, the rest are done by an identical method.

    The two points are (2, 4) and (-3, 1). The slope of the line between these points is, by definition:
    m = (y2 - y1)/(x2 - x1) where (x1, y1) and (x2, y2) are your two points.

    So
    m = (1 - 4)/(-3 - 2) <-- You can put the points into this equation in either order.

    m = -3/(-5) = 3/5.

    Now the form of the line will be
    y = mx + b

    y = (3/5)x + b

    Now we put one of the two points into this formula to find a value for the y intercept coordinate b. Either point may be used. I'll use (2, 4).

    4 = (3/5)*2 + b

    4 = 6/5 + b

    b = 4 - 6/5 = 20/5 - 6/5 = 14/5

    Thus your line is:
    y = (3/5)x + 14/5

    Just to check, let's put in the other point, (-3, 1).
    y = (3/5)x + 14/5

    1 = (3/5)*(-3) + 14/5

    1 = -9/5 + 14/5 = 5/5

    1 = 1 (Check!)

    -Dan
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