Consider the function $a(x)=3x-5$.  

1. What is the average rate of change of $a(x)$ over the interval $2\le x\le6$?

   Step (a):

   $\frac{a(6)-a(2)}{6-2}$

2. Repeat part (a) for the interval $5\le x\le7$.

   Step (b):

   $\frac{a\left(7\right)-a\left(5\right)}{7-5}$

3. What can you conclude from your answers to parts (a) and (b)? Why?

   Hint (c):

   Think about the graph of $y=a(x)$.
   What type of curve is it?