How do you write an interval in math?

Answer 1

Usually as a range in brackets. The curved brackets, ( and ), are used for "open" intervals, where the end points are not included. The square brackets, [ and ], are used for closed intervals where the end points are included. You can also have semi-closed brackets.

For example

x is in (3,5) is equivalent to 3 < x < 5

x is in [3,5] is equivalent to 3 ≤ x ≤ 5

x is in (3,5] is equivalent to 3 < x ≤ 5