Calculate the derivative, and determine the intervals where f ′ ( x ) > 0 {\textstyle f'(x)>0} and f ′ ( x ) < 0 {\textstyle f'(x)<0} . When f ′ ( x ) > 0 {\textstyle f'(x)>0} , f ( x ) {\textstyle f(x)} is increasing, while f ′ ( x ) < 0 {\textstyle f'(x)<0} , f ( x ) {\textstyle f(x)} is decreasing.
