If f(x) = 4ˣ , what formula will describe f(x)'s average

Last updated: 8/11/2022

If f(x) = 4ˣ , what formula will describe f(x)'s average value over the interval (-1, 3]? Don't evaluate the formula. If f(x) = x³ + 2x, what is the average value of f(x) over the interval (1, 3)?