# Is #x = 7# a function?

##### 1 Answer

#### Explanation:

In mathematics, a function is a relation between a set of inputs and a set of permissible outputs with the property that each input is related to exactly one output (See https://en.wikipedia.org/wiki/Function_%28mathematics%29#cite_note-1 for more information).

In most graphs with a x-axis and a y-axis, there is only one y-value for every x-value. Take for example

graph{y=x [-10, 10, -5, 5]}

Notice that as you keep going across the graph, the line always continues through the

However,

A **vertical line test** is often best used to determine a function of a curve. Common equations are inverse trigonometry equations like

Khan Academy has a good series on understanding functions in depth:

https://www.khanacademy.org/math/algebra/algebra-functions.