Find the intervals on which each of the following functions is (a) increasing (b) decreasing.
f(x)=3x4-4x3-12x2+5
f’(x)=12x3-12x2-24x
=12x(x2 -x-2)
=12(x)(x+1)(x-2)
Function f(x) is decreasing for x ∈ (-∞,-1] ∪ [0, 2] and increasing in x ∈ (-1,0) ∪ (2, ∞)
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