() is for < and >
[] is for ≤ and ≥
(a,b) means from a to b, not including a or b
(a,b] means from a to b, not including a, but including b
so
x<-3
so from -3 to less of that or
from -∞ to -3
you can't equal -∞, so we use parnthasees
also, it is < so we use parnthaees
(-∞,-3)
