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Math Help - confused :(

  1. #1
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    confused :(

    Ok, I am graphing P=(1,2) with slope m=3. This is how I worked out

    y-2=3(x-1)

    = y-2=3x-3

    = y=3x-3+2

    = y=3x-1

    If x=0 then;

    y=3(0)-1

    = y=-1

    and so (0,-1)

    this would be my second point no, or is this my run? In checking with the book's answer to see if I had done this right it showed my second point to be (2,5) with a run of 1 and a rise of 3......Did I do something wrong in the calculations!?


    Thanks!!
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  2. #2
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    You are right. When graphing a line by getting 2 points and drawing a line through them you can use any 2 points on a line. The book simply chose its points differently.
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  3. #3
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    Quote Originally Posted by badgerigar View Post
    You are right. When graphing a line by getting 2 points and drawing a line through them you can use any 2 points on a line. The book simply chose its points differently.
    .....oh, ok. So in this case, having my second points (0,-1) I can then find the run of the slope no?!

    Thanks !!!

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  4. #4
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    So in this case, having my second points (0,-1) I can then find the run of the slope no?!
    The run is the x-value of the 2nd point minus the x-value of the first point. The rise is the y-value of the second point minus the y-value of the first point.
    They are pretty much only useful to find the slope using m = \frac {rise}{run}
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