## Lecture Notes: Friday, October 9, 1998

Fifth Homework
Assignment - for discussion at recitations on** **Thursday October
8, Tuesday October 13, and Thursday October 15..

### Comments on Exam #2.

### Chapter 4

**Section 3 (Concavity and Points of Inflection)**
Concavity:
- Concave up -- f' increasing -- f" positive
- Concave down -- f' decreasing -- f" negative

Inflection point: means change of concavity.
- f" goes from negative to zero to positive or vice
versa.

- Application to extrema:
- f differentiable. c inside domain of f. f'(c) = 0, then:
- f"(c) > 0 -> c is local min
- f"(c) < 0 -> c is local max

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