Explain what the vertical line test is and how it is used.
The vertical line test is a way to determine if a graph represents a function. To use the vertical line test, you simply draw a vertical line at any point along the x-axis on the graph. If the vertical line intersects the graph in more than one point at any given x-value, then the graph does not represent a function. If the vertical line only intersects the graph at one point for all x-values, then the graph does represent a function.
In other words, if you can draw a vertical line that touches the graph at more than one point, the graph fails the vertical line test and is not a function. If the graph passes the vertical line test, it is a function. This test is useful in determining whether a given graph represents a function or not.