Which ordered pairs prevent this relation from being a function?

A relation is a function only if each x-value is paired with exactly one y-value. The pairs (1, 4) and (1, 3) assign two different outputs to x = 1, so they prevent the relation from being a function. Having the same y-value, as in (1, 3) and (–1, 3), is allowed when the x-values differ.

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