When working with quantitative relationships, three concepts help “set the stage” in your thinking as you seek to understand the relationship’s behavior: domain, range, and codomain.

### Domain

The “domain” of a function or relation is:

- the set of all values for which it can be evaluated
- the set of allowable “input” values
- the values along the horizontal axis for which a point can be plotted along the vertical axis

For example, the following functions can be evaluated for **any** value of “x”:

therefore their domains will be “the set of all real numbers”.

The following functions cannot be evaluated for all values of “x”, leading to restrictions on their Domains – as listed to the right of each one:

The values for which a function or relation cannot be Continue reading Domain, Range, and Codomain of a Function