Answer:
5
Step-by-step explanation:
The average rate of change of f(x) in the closed interval [ a, b ] is
[tex]\frac{f(b)-f(a)}{b-a}[/tex]
Here [ a, b ] = [ 4, 8 ] and from the graph
f(b) = f(8) = 10
f(a) = f(4) = - 10, hence
average rate of change = [tex]\frac{10-(-10)}{8-4}[/tex] = [tex]\frac{20}{4}[/tex] = 5
