The average rate of change is the gradient of the line joining the 2 end points.
Gradient is the change in f(x) divided by change in x.
What is the change in f(x) between x=5 and x=9 ?
What is the change in x between x=5 and x=9 ?
So what is the average rate of change?
Please no one answer over me. I am trying to teach!