Answer:

Explanation:
The domain is the span of x-values covered by the graph.
From the graph, we can see that the x-values covered by the graph is all values to the left of zero including zero.
Therefore, the domain is all x-values less than or equal to 0:

Further notes:
In interval notation, this is:
![(-\infty,0]](https://img.qammunity.org/2021/formulas/mathematics/high-school/8rvdr0hawer16rdg8oikg18oe4jps0ekda.png)