## Precalculus (6th Edition) Blitzer

$y$ is NOT a function of $x$
RECALL: If all vertical lines will pass through the graph in at most one point, then the graph represents $y$ as a function of $x$. Otherwise, the graph does not represent $y$ as a function of $x$. Notice that one vertical line (the line shown in the graph itself) will pass through the graph at infinitely many points. The graph fails the vertical line test. Thus, the given graph does not represent $y$ as a function of $x$.