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.
Ok, I am graphing P=(1,2) with slope m=3. This is how I worked out
If x=0 then;
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!?
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.So in this case, having my second points (0,-1) I can then find the run of the slope no?!
They are pretty much only useful to find the slope using