The closed interval `[a,b]` is the set of all real numbers `x` such that `alt= xlt= b` . This is written as,

`[a,b]={x in R| alt= xlt= b}`

This is usually written this simply as `{x | alt= xlt= b}` , and it is understood that `x` belongs to `R` .

## See eNotes Ad-Free

Start your **48-hour free trial** to get access to more than 30,000 additional guides and more than 350,000 Homework Help questions answered by our experts.

Already a member? Log in here.

**Further Reading**