Sal finds the intervals where g(x)=-x_+6x_-2x-3 is concave down/up by finding where its second derivative, g”, is positive/negative. Watch the next lesson: https://www.khanacademy.org/math/ap-calculus-ab/ab-derivatives-analyze-functions/ab-inflection-points/v/inflection-points-algebraically?utm_source=YT&utm_medium=Desc&utm_campaign=APCalculusAB Missed the previous lesson? https://www.khanacademy.org/math/ap-calculus-ab/ab-derivatives-analyze-functions/ab-justification-with-second-derivative/v/second-derivative-test?utm_source=YT&utm_medium=Desc&utm_campaign=APCalculusAB AP Calculus AB on Khan Academy: Bill Scott uses Khan Academy to teach AP Calculus at Phillips Academy in Andover, Massachusetts, and heÕs part of the teaching…