The equation y=mx+b is used to express the equations of lines. If given the points (1,2) and (3,4), first one must find the slope, which is expressed by the letter m. To find the slope, the equation is y2-y1 over x2-x1. To find this, we plug each number from the coordinates into the equation to get 4-2 over 3-1, or 2 over 2, which can be simplified to 1. Our equation is now y=1x+b. Pick one of the points and plug the coordinates into the equation. If we put (1,2) into the equation, it then looks like 2=(1)1+b. 1x1=1, so 2=1+b. Subtracting 1 from each side leaves us with b=1. y=1x+1. This can now be graphed.
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