Step-by-step explanation:
the average rate of change of a function f(x) between two values of x is
(f(x2) - f(x1)) / (x2 - x1)
f(x) = 20× (1/4)^x
x1 = 1
x2 = 2
f(x2) = 20× (1/4)² = 20/16 = 5/4
f(x1) = 20× (1/4)¹ = 20/4 = 5
(5/4 - 5) / (2 - 1) = (5/4 - 20/4) / 1 = -15/4
the average rate of change is -15/4.
