(1 point) Determine the intervals on which the function f(x) = -7x - 8 In (2x), (x > 0) is concave up or down and find the points of inflection. (Use symbolic notation and fractions where needed. Give your answer as comma separated list. Enter NULL if there are no points of inflection.) Points of inflection: help (fractions) (Use symbolic notation and fractions where needed. Give your answers as intervals in the form (*,"). Use inf for infinity , U for combining intervals, and appropriate type of parenthesis "(", ")", "[" or "]" depending on whether the interval is open or closed. Enter NULL if interval is empty.) f (x) is concave up when x E help (intervals) f(x) is concave down when x E help (intervals)