Vertical Line Test :

A curve in the $\"xy-\"$ plane is the graph of a function of $\"x\"$ if and only if no vertical line intersects the curve more than once.

Observe the graph.

Draw a vertical line along the $\"y-\"$ axis, the line touches the curve more than once.

The graph of the function fails the vertical line test.

Hence by the definition of vertical line test, the graph is not a function of $\"x\"$ .

No, the graph is not a function of $\"x\"$ .