The average rate of change can be found by striking a line between the two endpoints and finding the slope thereof:
[tex]ROC_{ave}=m_{1-2}[/tex]
[tex]m_{1-2} = \frac{f(x_2)-f(x_1)}{x_2-x_1} = \frac{f(3)-f(1)}{3-1}[/tex]
Solve for f(3) & f(1), substitute into the slope formula and compute.
[tex]m_{1-2} = \frac{9-3}{3-1}[/tex]
[tex]m_{1-2} = \frac{6}{2} = 3[/tex]
