Answer
a) $(-3;0)$ & $(3;\infty)$
b) $(-\infty;-3)$ & $(0;3)$
Work Step by Step
Step 1: Find critical points where f′(x)=0
Step 2: If f′(x) is positive, the function is increasing
Step 3: If f′(x) is negative, the function is decreasing
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