# What is an open interval?

##### 1 Answer

#### Answer:

See explanation...

#### Explanation:

If

In symbols we could write:

This reads

When we want to talk about all the Real numbers we may write:

#(-oo, +oo)#

The symbols

#-oo < x < +oo#

If we want to talk about any number greater than

#x in (5, +oo) " "# (#x# is in the open interval "#5# to plus infinity")

If we want to talk about any number less than

#x in (-oo, 5) " "# (#x# is in the open interval "minus infinity to#5# ")

If

The amalgamation of these two sets is called the union and is denoted:

#(-oo, 5) uu (5, +oo)#