Work Step by Step
A function is a relation in which each component of the domain corresponds to exactly one component of the range. In other words, if we define a relation in terms of x- and y-values, a function is a relation in which each x-value corresponds to exactly one y-value. We can use the vertical line test to determine if a graph is a graph of a function. If you draw a vertical line through the graph and this line intersects the graph more than once, this cannot be a graph of a function (as more than one intersection tells us that at least one x-value corresponds to more than one y-value).