Union means you take everything that was included in either individual interval.
The first interval goes from -1 to 1 (not including either endpoint).
The second interval goes from 0 to 6 (including both endpoints).
So, the first one starts at -1 and keeps going to the right, overlapping where the second one picks up and you keep going until you get to 6.
You still need to leave out -1 and include 6.
Answer: (-1,6]
