Answers:
- Not a function
- Not a function
- Function
- Not a function
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Explanation:
A function has any given input lead to exactly one output.
Relation 1 has the input "paper" lead to more than one output, which are the values 9 and -3. Therefore, relation 1 is not a function.
Relations 2 and 4 are similar stories.
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In contrast, relation 3 has each input lead to exactly one output, which is why we have a function here.
Put another way: a function cannot have the x coordinates repeat, but the y coordinates can repeat.
