# What is the vertical and horizontal line tests for 1-1 function?

##### 1 Answer

Mar 29, 2015

A graph of a 1-1 function needs to pass both the vertical line test and the horizontal line test.

A graph will represent a function, if any vertical line drawn crosses it only once. If the function is also 1-1, then any horizontal line drawn will cross it only once. If the horizontal line crosses the graph more than once, the function is not 1-1.