Answer:
(-∞, -1 )∪(3, ∞)
Step-by-step explanation:
Given function,
Differentiating with respect to x,
For increasing or decreasing,
f'(x) = 0
By quadratic formula,
In interval (-∞, -1 ), f'(x) = positive,
⇒ f(x) is increasing on (-∞, -1 ),
In interval (-1, 3), f'(x) = negative,
⇒ f(x) is decreasing on (-1, 3),
In interval (3, ∞), f'(x) = positive,
⇒ f(x) is increasing on (3, ∞),
