Question

Which relation is a function?
{(1, 4), (2, 2), (3, 5), (1, 7), (2, 9)}
{(1, 4), (2, 2), (3, 5), (4, 7), (2, 9)}
{(1, 4), (2, 2), (3, 5), (4, 7), (5, 9)}
{(1, 1), (2, 2), (1, 5), (2, 7), (5, 5)}

Answer 1

Which one does not repeat the X-values?

Answer 2

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