Vertical Line Test (Leaving Cert Mathematics): Revision Notes

Vertical Line Test

The vertical line test is used to determine whether a graph represent a function.

The following graph represents $y=x^2$.

The graph passes the vertical line test. That is, each vertical line passes the graph at most once.

If any vertical line intersects the graph more than once, the graph does not represent a function.

The equation of a circle is not a function.