# Question #ed9fd

##### 1 Answer

See below.

#### Explanation:

The following answer using definitions and notations like those in *Calculus* by James Stewart.

By definition: A function

The interval may be open, closed or half-open.

In many calculus classes and calculus textbooks, questions are phrased to ask students to find the open intervals on which a function is increasing and the open intervals on which it is decreasing.

For example

So

and on

A typical text question would say

**Other notation**

For the open interval I have denoted