Question

Is the relation a function?

{(-6, 1), (2, 3), (3, 4), (4, 5)}

Answer 1

The one you provided in your text: Yes, each input has exactly one output.

The second one: No. 3 has two outputs.

The third one: No, two outputs for each x>-4.

The fourth one: Yes, unique y for each x.