Find the x-values where points of inflection occur occur. State the x-intervals where the function is concave up and the x-intervals where it is concave down. f(x) = -x +6x2 -15 Submit a complete written solution for this problem, being sure to show all your intervals and test values and how you tested each value. What are the x-values of the inflection point(s)? O A. The x-values of the inflection point(s) are x = (Use a comma to separate answers as needed.) O B. There are no inflection points. On what x-interval(s) is f concave up or concave down? O A. f is concave up on ( - co,0) and (4,co). f is concave down on (0,4). O B. f is concave up on ( - co,2) and (2,co). f is never concave down. O C. f is concave up on (2,co). f is concave down on ( - co,2). O D. f is concave up (0,4). f is concave down on ( - co,0) and (4,00). O E. f is concave up on ( - co,2). f is concave down on (2,co). O F. f is never concave up. f is concave down on ( - co,2) and (2,co)