To determine the intervals on which the function is increasing, we can analyze the behavior of the graph:
- From negative infinity up to the cusp at (-1, 0), the function is moving downwards towards the cusp, so it is not increasing.
- Between the cusp at (-1, 0) and the local maximum at (0, 1), the function is increasing.
- Between the local maximum at (0, 1) and the cusp at (1, 0), the function is again decreasing, hence not increasing in this interval.
- After the cusp at (1, 0), the function continues to increase until it goes to infinity.
Based on this analysis, the function is increasing on the intervals:
- From (-1, 0) (not including the endpoints, as they are cusps where the function is neither increasing nor decreasing)
- From (1, infinity).
Thus, the correct answer is: left-parenthesis negative 1 comma 1 right-parenthesis union left-parenthesis 1 comma infinity right-parenthesis.