Can someone please help me?
Which of the following relations is a function?

{ (1, 2), (1, 3), (2, 8), (3, 9) }

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

{ (3, -1), (2, 3), (3, 4), (1, 7) }

{ (3, 0), (4, -3), (6, 7), (4, 4) }

Question

Can someone please help me?
Which of the following relations is a function?

    { (1, 2),  (1, 3),  (2, 8),  (3, 9) }

    { (1, 2),  (2, 3),  (3, 4),  (4, 5) }

    { (3, -1),  (2, 3),  (3, 4),  (1, 7) }

    { (3, 0),  (4, -3),  (6, 7),  (4, 4) }

anonymous · Answer

a function is when every x has one y
so the second one is a function