calculus
posted by Magnus .
f(x)=  2x^3 + 45x^2 300x +9
There are 3 intervals (inf,A], [A,B], [B, inf) where A and B are critical points.
Find A and B?
For each of the intervals is it decreasing or increasing??
I found the derivative which is 6x^2+90x300
6(x^215x +50)
(x5)(x10) so I thought the critical points would be 5 and 10 but that's not what my book says??

Nevermind I got it!