How do you find the average gradient between two points on a curve?

Read off the x and y values of each point. Call them x1, x2, y1 y2. Then average gradient=(y2-y1)/(x2-x1).

The average gradient between two points on a curve is the gradient of the straight line that passes through the points

If point 1 has the co-ordinates (a, b) and point 2 has the co-ordinates (c, d) then the average gradient will be (d - b)/(c - a).