Recall that the average rate of change between a and b is given by the following formula:
[tex]\frac{f(a)-f(b)}{a-b}\text{.}[/tex]
From the graph we get:
[tex]\begin{gathered} f(4)=-1, \\ f(8)=-9. \end{gathered}[/tex]
Therefore, the average rate of change from x=4 to x=8 is:
[tex]\frac{f(4)-f(8)}{4-8}=\frac{-1-(-9_{})}{-4}=\frac{-1+9}{-4}=\frac{8}{-4}=-2.[/tex]
Answer: -2.
