Question

F = {(6, 3), (5, 4), (4, 5), (3, 6), (2, 7)} Is F a function and why?

Yes, no two ordered pairs in this list has the same first element.
Yes, no two ordered pairs in this list has the same second element.
Yes, there is more than one ordered pair in this list.
No, there is a limited number of ordered pairs in this list.

Answer 1

Yes, no two ordered pairs in this list has the same first element
Remember the x-value is the important one, if there are repeated x-values then it is not a function but rather a relation...

Hope this helps :)