Question 1169878
f'(x)=-6x^2+6x+36
set that equal to 0
6x^2-6x-36=0, multiplying by -1
x^2-x-6=0 dividing by 6 both sides
(x-3)(x+2)=0
x=-2, 3
-2

{{{graph(300,300,-3,5,-100,100,-2x^3+3x^2+36x)}}}