A relation is only a function if ALL the x-values (the first number in the pairs) ONLY have one partner.
Check that -1
At first that -1 is paired up with a 5 in the ordered pair (-1, 5) but then later... that -1 is down there hanging out with a 1 in the last ordered pair (-1, 1).
This means that this relation (all the pairs lumped together) is NOT a function. Just because of that -1 pairing up with more that one partner.
