For the function f(x) = x3 −12x + 8, find all intervals where the function is increasing: f is increasing on (Give your answer as an interval or a list of intervals, e.g., (-infinity, 8] or (1, 5), (7, 10).) Similarly, find all intervals where the function is decreasing: f is decreasing on, (Give your answer as an interval or a list of intervals, e.g., (-infinity, 8] or (1, 5), (7, 10).)
Finally, find all critical points in the graph of f(x) critical points: x = (Enter your x -values as a comma-separated list, or none if there are no critical points.)