Answer:
-∞ < x < 0
Explanation:
The domain is the horizontal extent of the graph.
The arrow at upper left means the graph extends to infinity upward and to the left.
The open circle on the y-axis means the value x=0 is not included in the domain.
So, the graph extends from -∞ to as close to zero as you like:
domain: -∞ < x < 0