Find the intervals on which the function 
is
(a) strictly increasing (b) strictly decreasing.
f(x)=2x3-3x2-36x+7
f’(x)=6x2-6x-36
f’(x)=6(x2-x-6)
f’(x)=6(x-3)(x+2)
f’(x) is 0 at x=3 and x=-2
F’(x)>0 for x ∈ (-∞, -2] ∪ [3, ∞)
hence in this interval function is increasing.
F’(x)<0 for x ∈ (-2 ,3)
hence in this interval function is decreasing.
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