This is where students usually sweat. An open circle means the point is not included. A closed circle means it is. In Desmos, you use inequalities: < or > for open; <= or >= for closed.
Mistype a sign? Your graph will look like it has a tiny hole, like a donut missing a sprinkle. Fix it by changing < to <= in the condition. Desmos updates instantly. Magic, I tell you.
