Find the largest open intervals on which the function is concave upward or concave downward, and find the location of any points of inflection. f( x) =2x*+ 12x- 216x-+24x-9 Select the correct choice below and fill in the answer box(es) to complete your choice. (Type your answer in interval notation. Use a comma to separate answers as needed. Use integers or fractions for any numbers in the expression.) A. The function is concave upward on and concave downward on B. The function is concave downward on . There are no intervals on which the function is concave upward. Q. The function is concave upward on There are no intervals on which the function is concave downward