Find the intervals on which each of the following functions is (a) increasing (b) decreasing.
f’(x)=(12x3-24x2-60x+72)/10
=1.2(x3-2x2-5x+6)
=1.2(x-1)(x-3)(x+2)
Function f(x) is decreasing for x ∈ (-∞,-2] ∪ [1, 3] and increasing in x ∈ (-2,1) ∪ (3, ∞)