1. [1.5/4 Points] DETAILS PREVIOUS ANSWERS Consider the equation below. (If an answer does not exist, enter DINE.) ((x) =x3-9x2-21x +9 (a) Find the Interval(s) on which / is increasing. (Enter your answer using interval notation.) Find the interval(s) on which f is decreasing. (Enter your answer using interval notation.) (b) Find the local minimum and maximum values of f. local minimum value local maximum value (c) Find the inflection point. ( x , y ) = Find the interval(s) on which f is concave up. (Enter your answer using interval notation.) Find the interval(s) on which f is concave down. (Enter your answer using interval notation.)