Vertical Line Test

1
Vertical Line Test
2
Warm-Up
Graph each of the relation and tell whether it is
a function
1.
2.
3.
4.
X Y
1 5
3 4
2 3
5 4
6 5
X Y
1 5
3 4
2 3
1 4
4 5
3
1
X Y
1 5
3 4
2 3
5 4
6 5
We know it is a function because non of the x
values in the table repeat. We can also hold a
vertical line up to the points and see that no 2
points are touched by the same vertical line
This method of determining a function from a
graph is know as the vertical line test
4
2
First create a table of values
X Y
-2 -6
-1 -5
0 -4
1 -3
2 -2
Next graph the points and draw the line or curve
if not linear
Run vertical line across the graph and see if it
touches two places at the same time
5
3
X Y
1 5
3 4
2 3
1 4
4 5
Notice the two points that are touched by the
green line. This means that the relation is not a
function
6
4
First create a table of values
X Y
4 -2
1 -1
0 0
1 1
4 2
Next graph the points and draw the line or curve
if not linear
Run vertical line across the graph and see if it
touches two places at the same time
The relation fails the vertical line test
touches in 2 places and thus is not a function