#### Answer

In the graph by the vertical line test, $y$ is a function of $x$.

#### Work Step by Step

According to the vertical line test, if there is any intersection by any vertical line on a graph at more than one point (that is, for one value of x, there is more than 1 value of y), then the graph cannot be defined as y as a function of x.
In graph, for one value of x, there is only 1 value of y. Thus the graph passes the vertical line test. Therefore, $y$ is a function of $x$.
Hence, $y$ is a function of $x$.