### Home > CALC > Chapter 8 > Lesson 8.3.3 > Problem 8-129

8-129.

Recall that candidates for points of inflection occur where the 2nd-derivative equals zero AND where the 2nd-derivative does not exist.

After you identify where *f* ''(*x*) = 0 and where *f* ''(*x*) = DNE, check the regions before, after and between those candidates: if *f* ''(*x*) > 0, then *f*(*x*) is concave up.