Write the set of points from -3 to -1 but excluding -2 and -1 as a union of intervals:
https://www.mathsisfun.com/sets/intervals.html
[-3,-2)U(-2,-1)
check that with the web link above. Not all teachers, nor text make the distinction of [ and )
To write the set of points from -3 to -1, excluding -2 and -1, as a union of intervals, we can split it into two intervals:
First interval: (-3, -2)
In this interval, we exclude -3 and include -2, so it is an open interval.
Second interval: (-2, -1)
In this interval, we exclude -2 and -1, so it is an open interval as well.
Combining these two intervals, we write the set of points from -3 to -1 excluding -2 and -1 as a union of intervals: (-3, -2) U (-2, -1).