Third-degree polynomial usually has 1 relative maximum and 1 relative minimum, or they don't have a relative maximum or minimum. Looking at the graph we can see that there's one relative maximum and one relative minimum.
The relative minimum is near x = 1, and the relative maximum is near x = 3. There are 1 relative maximum and 1 relative minimum
The increasing interval will be the interval between the relative minimum and the relative maximum, then, approximately the interval (1.2, 2.8), that's the increasing interval
The decreasing interval will be any other value removing the increasing interval, then, we can write the decreasing interval as
