Vertical Line Test

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In this lesson, we learn how to use the vertical line test to determine if a relation represents a function. We previously learned that a function was a relation where each x-value or member of the domain is associated with one y-value or member of the range. So when we think about this concept graphically, we can say that no vertical line should impact the graph of a function in more than one location. This is due to the fact that a vertical line always has the same x-value. If a vertical line impacts the graph of a relation in more than one location, then the relation is not a function. This is because the single x-value associated with the vertical line is linked up with more than one y-value, which violates the definition of a function.
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