First find the values of f(x) for x = 1 and for x = 3.
Reading off the graph they are f(x) = 3 and f(x) = 9 respectively.
You could also have found thess values by substitution of x in f(x) - eg for x = 1 f(x) = 2^1 + 1 = 3.
Average rate of change = difference in f(x) / difference in x = (9 - 3) / (3 - 1) = 6/2 = 3 answer
