Let f (x) = - log (4x) + 5.

What is the average rate of change of f (x) from 3 to 8?

Round your answer to the nearest hundredth.

To solve the average rate of change, use the formula of the slope:

m = (y2 - y1) / (x2 - x1)

but first we must solve the value of the function when x = 3

f (3) = - log (4 * 3) + 5

f (3) = 3.92

solve the function when x = 8

f (8) = - log (4 * 8) + 5

f (8) = 3.49

so the average rate of change

m = (3.49 - 3.92) / (8 - 3)

m = - 0.09