Answer:
there are two of the same x-values (1) and for something to be a function x cannot repeat.
Explanation:
There are two different y-values assigned to the same x-value.
A function may not have two y-values assigned to the same x-value.
(1,7) and (1,-1) have two different y-values (7 and -1) assigned to the same x-value (1).
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