u find the slope of the two points, and that is the rate of change. the slope equation is y2-y1/x2-x1 ,, so for example, if you have the points (3,1) and (4,6) the equation you would do is 6-1/4-3 , which is equal to 5/1 (aka 5) , therefore the rate of change (and slope) is 5
