Slope is the ratio of the vertical and horizontal changes between two points on a surface or a line.The vertical change between two points is called the rise, and the horizontal change is called the run.The slope equals the rise divided by the run: .This simple equation is called the slope formula. If y=f(x+h)=3(x+h)2. (Just plug x+h in for x). So, you get figure (ii). The instantaneous rate of change, or derivative, can be written as dy/dx, and it is a function that tells you the instantaneous rate of change at any point. y′=f′(x+h)=(ddx)(3.(x)2)=6x.1=6x For example, if x=1, then the instantaneous rate of change is 6. Rate of Change Formula helps us to calculate the slope of a line if the coordinates of the points on the line are given. ... If coordinates of any two points of a line are given, then the rate of change is the ratio of the change in the y-coordinates to the change in the x-coordinates.