Consider the equation below. (If an answer does not exist, enterDNE.) f(x) = x3 − 9x2 − 21x + 9
(a) Find the interval on which f is increasing. (Enter youranswer using interval notation.) Find the interval on which f isdecreasing. (Enter your answer using interval notation.)
(b) Find the local minimum and maximum values of f. localminimum value local maximum value
(c) Find the inflection point. (x, y) = Find the interval onwhich f is concave up. (Enter your answer using interval notation.)Find the interval on which f is concave down. (Enter your answerusing interval notation.)
