Step-by-step explanation:
The ends of the interval are written as an ordered pair, left end first. The parentheses used are dependent upon whether the end is included in the interval. If not, the corresponding bracket is curved, ( ). If an end value is included in the interval, the corresponding bracket is square, [ ].
Here are some examples:
-1 < x < 6 . . . . (-1, 6)
43 ≥ x > 2 . . . (2, 43]
-6 ≤ x < ∞ . . . . [-6, ∞)
13 ≤ x ≤ 14 . . . [13, 14]
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When infinity (∞) is involved, the bracket is always curved. There is no number that is equal to infinity.