Need help on math question. - BasilMarket Forum

thread starter Johasua Aug 14 2010 + PM | QUOTE | PERMALINK | REPORT

Hello, I was going through my Calculus and Vectors textbook, and I found this question that I'm stuck on. (it's in the chapter about derivatives and stuff if it matters) For what values of x does the curve y= -x^3 + 6x^2 have a slope of -12? (I hope I wrote that right) The answers in the back says: 2 + - 2 sqrt2 (So 2 + or - 2 square root 2) I'm not sure if I'm supposed to get the derivative of it or not, and then what to do after that. Please include an explanation if you can. Thanks

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djpinc19 08/14/10 + PM | QUOTE | PERMALINK | REPORT

Derive y. Set y' equal to -12. Solve for x. By solving for x, we are looking for the point along the horizontal axis where the slope in the original function is -12. y = -x^-3 + 6x^2 y' = 3x^-4 + 12x -12 = 3x^-4 + 12x and so on

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