Answers:
- Function
- Not a function
- Function
- Not a function
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Explanation:
If x repeats itself, then we don't have a function. For instance, relation 2 has the x value -4 show up twice. That input leads to multiple outputs which is why we don't have a function. Relation 4 is a similar story (this time the input 'u' shows up twice).
Relations 1 and 3 don't have this issue, so they are functions.
