Question

Find the average rate of change for f(x) = x2 + 9x + 18 from x = −10 to x = 10. A) 3 B) 7 C) 9 D) 11

Answer 1

C

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 ] = [ - 10, 10 ], thus

f(b) = f(10) = 10² + 9(10) + 18 = 100 + 90 + 18 = 208

f(a) = f(- 10) = (- 10)² + 9(- 10) + 18 = 100 - 90 + 18 = 28, thus

average rate of change =
`(208-28)/(10-(-10))` =
`(180)/(20)` = 9