Find the largest open interval(s) on which f is decreasing. (If two open intervals are equally large enter your answer as a comma-separated list of intervals.)
The x y-coordinate plane is given. The curve begins at the origin, goes up and right, changes direction at the point (4, 8), goes down and right, changes direction at the point (8, 5), goes up and right, changes direction at the point (9, 6), goes down and right, and stops at the point (10, 3).