For more help check out:
http://www.youtube.com/watch?v=Q81gafPM5y8
http://www.youtube.com/watch?v=c1N8zyVhWxM
http://www.khanacademy.org/math/calculus/differential-calculus/v/inflection-points-and-concavity-intuition
http://www.cliffsnotes.com/study_guide/Concavity-and-Points-of-Inflection.topicArticleId-39909,articleId-39894.html
Homework: Make sure you have completed all of the book assignment 3.3. Start working on book 3.4. You will have time in class tomorrow to work on book 3.4.