Answer: all real numbers greater than or equal to -3
Step-by-step explanation:
The left-most point is at (-3,-2). The x coordinate is all we're concerned with here. The x coordinate for this point is x = -3. This is the smallest x value possible as an input. We cannot have x = -4 as that is nowhere on the blue curve.
So the domain is the set of real numbers x such that x is -4 or larger
In set builder notation, that would look like

In interval notation, we would say
to indicate to the reader "have an interval from -3 to positive infinity; include the endpoint -3"