The average rate of change of the function f (x) = 4x^3 + 4 over the interval [66 ,88 ] is

Average rate of change = [f (x₂) - f (x₁) ] / (x₂-x₁)

Interval [66,88] which is x₁=66, x₂=88

f (x) = 4x³+4

f (x₁) = f (66) = 4 (66) ³+4=1149988

f (x₂) = f (88) = 4 (88) ³+4=2725892

Average rate of change = 2725892-1149988/88-66

=1575904/22

=71632