Question

Does this graph show a function? Explain how you know.

Answer 1

Answer: B) No, the graph fails the vertical line test

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Explanation:

Ask yourself "is it possible to draw a vertical straight line through more than one point on the red graph?". In this case, the answer is "yes".

For instance, we could draw a vertical line through x = 3 and have that vertical line cross the red graph more than once. This means the x input x = 3 leads to more than one y output. We say the graph fails the vertical line test, and this graph is not a function.

A function is only possible if any x input leads to exactly one y output. The x value must be in the domain.