9514 1404 393
Answer:
(-1, 1)
Step-by-step explanation:
Find the differences between an f(x) value and the previous one
3 -18 = -15
0 -3 = -3
3 -0 = 3
6 -3 = 3
3 -6 = -3
Where the differences are positive, the function is increasing on the interval. Here, it is increasing on the intervals (-1, 0) and (0, 1). Then the longest increasing x-interval is (-1, 1).
