Answer
(a) is increasing on the interval $(0, +\infty)$;
(b) has no interval where it is decreasing;
(c) constant on the interval $(-\infty, 0)$
Work Step by Step
Based on its graph, the given function:
(a) is increasing on the interval $(0, +\infty)$;
(b) has no interval where it is decreasing;
(c) constant on the interval $(-\infty, 0)$