Answer:
1. not a function
Since x=5 produces y=9 and y=0, it can't be a function
2. it is a function because there is one value of y for every value of x
3. A circle is not a function. because it doesn't pass the vertical line test
4. I think is d but not sure has been a while since I have done these questions so sorry if I am wrong :)
Explanation:
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