When do you use the brackets [ x, y ] and when do you use the parenthesis ( x, y) when writing the domain and range of a function in interval notation?

1 Answer
MoominDave
Jun 20, 2018

It tells you whether the end point of the interval is included

Explanation:

The difference is whether the end of the interval in question includes the end value or not. If it includes it, it is called "closed", and is written with a square bracket: #[# or #]#. If it doesn't include it, it is called "open", and is written with a round bracket: #(# or #)#.

An interval with both ends open or closed is called an open or closed interval. If one end is open and the other closed, then the interval is called "half-open". For example, the set #[0,1)# includes all numbers #x# such that #x>=0# and #x<1#.

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