http://www.larsoncalculus.com/etf6/content/calculus-videos/chapter-4/section-4/concavityandinflectionpoints/#content-top
http://www.larsoncalculus.com/etf6/content/calculus-videos/chapter-4/section-4/determinetheconcavityandtheinflectionpoints/#content-top
http://www.larsoncalculus.com/etf6/content/calculus-videos/chapter-4/section-4/thesecondderivativetest/#content-top
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