Domain are all the x - values included in the graph.
In this case all the x - values are (listed from smallest to largest and excluding duplicates):
{-3, -2, 0, 1}
^^^This is also your domain
NOTE: There are several different ways to write domain. Let me know if this is the way you need it to be written in
Hope this helped!
~Just a girl in love with Shawn Mendes