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Math Help - Finding X in y = mx + b equations

  1. #1
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    Finding X in y = mx + b equations

    Hello:

    I am doing a math worksheet that I was given by my teacher, the sheet is full of slope problems. y = mx + b. You are given two points:

    Example:

    (4,1) (5,3) and you have to find what Y = and my answer was Y = 2x - 7
    ------------------------------

    There are two equations on here where it says X = for the answer instead. The two points are (4,1) and (4,13).

    Hopefully I am not being too confusing, thanks in advance for any help.
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  2. #2
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    Quote Originally Posted by CzWJF41 View Post
    Hello:

    I am doing a math worksheet that I was given by my teacher, the sheet is full of slope problems. y = mx + b. You are given two points:

    Example:

    (4,1) (5,3) and you have to find what Y = and my answer was Y = 2x - 7
    Hi there

    m = \frac{y_2-y_1}{x_2-x_1} = \frac{3-1}{5-4} = \frac{2}{1} = 2

    with

    y = mx + b

    is now

    y = 2x + b

    so far so good.

    Now use either point to find b. Using (4,1) gives

    1 = 2\times 4 + b

    b=-7 so y = 2x -7

    Good news for you!
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  3. #3
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     (4,1) and  (4,13) are on the line  x = 4 .

    You may sketch these two points in a coordinate system and construct a line through them, and as it can be seen this line is actually perpendicular to the x-axis.

    That means, all points designated as (4, a) (a can be any real number) are on the line because they all satisfy the condition that x = 4, given that there is nothing required for y.
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