Interval notation uses an ordered pair inside brackets. The ordered pair is ...
... lower end of the interval, upper end of the interval
The brackets are square if the endpoint is included (solid dot, or "≤"), and they are curved (parentheses) if the endpoint is not included (open dot, or "<"). The brackets don't have to match.
Here, your interval is -4 ≤ x ≤ -1, so we use square brackets around the end values -4 and -1.
... [-4, -1]
