Question

In an interval notation represent the set of real numbers

Answer 1

Interval notation is a way of writing the subsets of the real number line.

There are 2 types of brackets used to represent two types of intervals on the number line.

A closed interval is one that includes its endpoints. Closed brackets, [ ], are used to write out the intervals. For example, the interval 0 ≤ x ≤ 3 is represented as:

`\lbrack0,3\rbrack`

An open interval is one that does not include its endpoints. Open brackets, ( ), are used in this case. For example, the interval 0 < x < 3 is represented as:

`(0,3)`

The interval in the question is given to be:

`(-\infty,-1\rbrack`

This means that the interval contains all real numbers less than or equal to 1:

`x\le-1`

ANSWER: The answer is "less than or equal to".