Originally Posted by
Chris L T521 The average rate of change is defined as $\displaystyle \frac{f(b)-f(a)}{b-a}$
In your case, you need to evaluate $\displaystyle \frac{f(3)-f(1)}{3-1}$, where $\displaystyle f(x)=3x^2+1$
Can you take it from here?
--Chris