hi guys i'm stuck on this, i keep thinking i have the right answeres but i can't get them.(adsbygoogle = window.adsbygoogle || []).push({});

the function is f(x): -2x^3 + 39x^2 - 180x + 1

i need to list all of the critical points, and hten indicate where it is increasing and where it is decreasing.

I set the derivative -6x^2 + 78x - 180 = 0 and then solved for x. this is correct right. by doing so i ended up with critical points at -2 and 15. Then made a number line and figured that the slope before -2 was neg, b/w -2 and 15 it was pos, and after 15 it was neg. so my interval of increasing was (-2,15) and the interval of decreasing was (-inf, -2) U (15,inf) where am i going wrong - PLEASE HELP ME

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# Critical points

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