15. [11 Points] DETAILS 02'100 Submissions Used 2 Suppose the second derivative of x) is given by FIX) = (50%)? Determine the intervals of concavity of x). 49 X 0 x) is concave up on [00,2} U (2,00) and concave down on [2,2}. 0 x) is concave up on {22} and concave down on [00,2} U (2,00). 0 x) is concave up on (00,?) and concave clown on (7,00). 0 x) is concave up on (7,?) and concave down on [00,7} U (7,00). 0 x) is concave up on [00,7} U (7,00) and concave down on [7,7}