Danielle, Interval Notation - Here is an easier way of understanding intervals

Interval Notation:  (description) (diagram) Open Interval:   (a, b)  is interpreted as a < x < b  where the endpoints are NOT included.(While this notation resembles an ordered pair, in this context it refers to the interval upon which you are working.) (1, 5) Closed Interval:  [a, b]  is interpreted as a < x < b  where the endpoints are included. [1, 5] Half-Open Interval:  (a, b]  is interpreted as a < x < b where a is not included, but b is included. (1, 5] Half-Open Interval:  [a, b) is interpreted as a < x < bwhere a is included, but b is not included. [1, 5) Non-ending Interval:   is interpreted as x > a where ais not included and infinity is always expressed as being "open" (not included). Non-ending Interval:   is interpreted as x < b whereb is included and again, infinity is always expressed as being "open" (not included).