How do you use the vertical line test to determine whether #{(3,-1), (-2,3), (-1,-5), (3,2)}# is a function?

1 Answer
Nov 6, 2016

By definition, in a function, there is only ONE y-value for each x-value.

The vertical line test is used if you have a graph, or if you have plotted the points. A vertical line has the equation #x =n#

If the line intersects the graph more than once, the graph is not a function.

In this case, when #x=3#, there are two possible values for y.
#y = -1 # OR #y =2# (there is a choice of y-values.)

Therefore these points do NOT represent a function.