Find the average rate of change for the function between the give values.

Question

f(x)=-4x + 8; from 1 to 2

Answer 1

A. evaluate the function at x = 2
B. evaluate the function at x = 1
then
Subtract B from A
divide by the change in x from 1 to 1 which is 2-1 = 1
So the answer is simply
(A-B)

Answer 2

The book has the correct answer at -4..how'd they arrive at that?

Answer 3

A -4(2)+ 8 = 0
B -4(1)+ 8 = 4
A-B = 0 - 4 = -4