Use parentheses `( )` for endpoints not included
Use brackets `[ ]` for endpoints included
Use `∞` or `-∞` with parentheses only
Write the lower endpoint first, then the upper endpoint
Use a comma between the endpoints
Example: `(2, 5)` means greater than 2 and less than 5
Example: `[2, 5]` means between 2 and 5, including both endpoints
Example: `(−∞, 3]` means all numbers less than or equal to 3
Example: `[4, ∞)` means all numbers greater than or equal to 4
For unions, use `∪`
Example: `(-∞, 1) ∪ (3, ∞)`