Observe the graph :

The function is .

is increasing on , decreasing on , decreasing on , and increasing on .

Support numerically :

Construct the table of values by using the -values in each interval.

The interval :

Observe the above table, is increasing on .

The interval :

Observe the above table, is decreasing on .

The interval :

Observe the above table, is decreasing on .

The interval :

Observe the above table, is increasing on .

is increasing on , decreasing on , decreasing on , and increasing on .