Let f(x) = x + 3x - 9x + 15.(a) Use the definition of a derivative or the derivative rules to findf'(x)=(b) Use the definition

Let f(x) = x³ + 3x² - 9x + 15.(a) Use the definition of a derivative or the derivative rules to findf'(x)=(b) Use the definition of a derivative or the derivative rules to findf''(x) =(c) On what interval is f increasing (include the endpoints in the interval)?interval of increasing =(d) On what interval is f decreasing (include the endpoints in the interval)?interval of decreasing =(e) On what interval is f concave downward (include the endpoints in the interval)?interval of downward concavity =(f) On what interval is f concave upward (include the endpoints in the interval)?interval of upward concavity =