An example of a relationship that is not a function

The equation

x = y²

is not a function because both (1,1) and (1,-1) satisfy the

equation, and a function by definition cannot have two

different y-values for the same x value.

To make a graph of y² = x, make a table of values:

x | y

9 | 3

9 |-3

4 | 2

4 |-2

1 | 1

1 |-1

0 | 0