Find the intervals on which each of the following functions is (a) increasing (b) decreasing.
f(x)=x3-6x2+9x+10
f’(x)=3x2-12x+9
f’(x)=3(x2-4x+3)
=3(x-3)(x-1)
Function f(x) is decreasing for x ∈ [1,3] and increasing in x ∈ (-∞,1) ∪ (3, ∞)