Let f(x) = In (x4 + 432) . Answer the following questions. 1. Find the interval (s) on which f is increasing. Answer (in interval notation): 2. Find the interval(s) on which f is decreasing. Answer (in interval notation): 3. Find the local maxima of f. List your answers as points in the form (a, b), or say "none" if there are none. Answer (separate by commas): 4. Find the local minima of f. List your answers as points in the form (a, b), or say "none" if there are none. Answer (separate by commas): 5. Find the interval(s) on which f is concave upward. Answer (in interval notation): 6. Find the interval(s) on which f is concave downward. Answer (in interval notation)