Concavity f is concave up if f’ is increasing on an open interval. f is concave down if f’ is decreasing on an open interval.
Concavity Logically: If f’’ > 0 then f’ is increasing. If f’ is increasing, then f is concave up on the open interval. Therefore, if f’’ > 0 then f is concave up on the open interval.
Concavity
Point of Inflection
Basically, just like critical points are found when f’ is 0 or DNE, points of inflection are found when f’’ is 0 or DNE. Also, just like f is increasing or decreasing when f’ is >0 or 0 or <0.
Point of Inflection
Second Derivative Test