Question

Find the average rate of change between f(-7) and f(-1) in the function f(x)=x^2+2x -8

Answer 1

- 6

Explanation:

The average rate of change of f(x) in the closed interval [ a, b ] is

`(f(b)-f(a))/(b-a)`

here [ a, b ] = [ - 7, - 1 ]

f(b) = f(- 1) = (- 1)² + 2(- 1) - 8 = 1 - 2 - 8 = - 9

f(a) = f(- 7) = (- 7)² + 2(- 7) - 8 = 49 - 14 - 8 = 27

Hence

average rate of change =
`(-9-27)/(-1-(-7))` =
`(-36)/(6)` = - 6