explain what the vertical line test is and how it is used.

Brief Explanations:

The vertical - line test is a graphical method in mathematics. It is used to determine if a relation is a function. If any vertical line drawn on the graph of the relation intersects the graph at most once, then the relation is a function. This is because for a relation to be a function, each input (x - value) must have exactly one output (y - value). When a vertical line intersects a graph at more than one point, it means there is an x - value with multiple y - values, so it's not a function.

Answer:

The vertical line test is a graphical method to check if a relation is a function. It is used by drawing vertical lines on the graph of the relation. If any vertical line intersects the graph at most once, the relation is a function; if a vertical line intersects the graph at more than one point, the relation is not a function.