Question

when doing the second derivative test, do you set f''(x) to zero or plug in x values of f'(x)?

Answer 1

you plug in the critical values found by f'(x)
if f''(x) > 0 then its a minimum
if f''(x) <0 then its a maximum
if f''(x)=0 it is inconclusive and you have to do either the first order test or go into third order derivatives to determine whether it is a minimum, maximum or inflexion

Answer 2

The critical values being where f'(x) = 0

Answer 3

thank you!

Answer 4

No prob :)