# Can someone help me please? I need to find which of these is a function and I have no clue which is the answer.

Jun 26, 2018

Only the fourth example is a function.

#### Explanation:

What you need to look at is whether there are any values of the independent variable $x$ which map onto more than one dependent variable $y$. To be a function there can not be any duplication,

In the first example
$\textcolor{w h i t e}{\text{XXX}} 3$ is mapped onto both $- 5$ and $0$
So it is not a function.

In the second example
$\textcolor{w h i t e}{\text{XXX}} - 1$ is mapped onto both $- 11$ and $5$
So it is not a function.

In the third example
$\textcolor{w h i t e}{\text{XXX}} 3$ is mapped onto both $14$ and $19$
So it is not a function.

In the fourth example
$\textcolor{w h i t e}{\text{XXX}}$There is no place where two points (values of $y$)
$\textcolor{w h i t e}{\text{XXX}}$are identified (mapped from) any value of $x$
So it is a function.