### Home > CALC > Chapter 6 > Lesson 6.5.1 > Problem 6-171

6-171.

Remember to investigate all extrema CANDIDATES. That means, find all values of *x* where *f*'(*x*) = 0 AND *f* '(*x*) DNE.

After all, a max or min could exist at a cusp... But remember, sometimes these candidates turn out to be inflection points instead.

When looking for points of inflection, remember to consider where concavity changes. This could happen where *f* ''(*x*) = 0

or where *f* ''(*x*) = DNE.