Determine the intervals over which f x x4 4x 12 is increasing or decreasing O O O O a f x is decreasing on 3 f x is increasing on 3 b f x is decreasing on 0 3 f x is increasing on 3 c f x is decreasing on 0 U 0 3 f x is increasing on 3 d f x is decreasing on 0 3 00 f x is increasing on 0 3