### Home > CALC > Chapter 8 > Lesson 8.2.2 > Problem 8-84

8-84.

Concavity change might (or might not) happen where *f*''(*x*) = 0. Remember, you must confirm that concavity CHANGES at that candidate by detecting a sign change in the 2nd-derivative before and after the candidate, or by confirming that 3rd-derivative at the candidate is not equal to 0.