Question

Given f ′(x) = (5 – x)(8 – x), determine the intervals on which f(x) is increasing or decreasing.

Answer 1

first find when f'=0

Answer 2

then test each interval around the numbers that make f'=0

Answer 3

if f'>0 then f is increasing
if f'<0 then f is decreasing

Answer 4

5 and 8?

Answer 5

yep

Answer 6

you have three intervals to test

Answer 7

choose a number representative from each interval and plug into f'

Answer 8

What?

Answer 9

choose a number from each interval and plug into f'

Answer 10

I'm not sure how else to say it