Question: Which of the following relations on the set of integers is not a function?

Options:

1. R1 = {(1, 2), (1, 3)}
2. R2 = {(2, 3), (3, 4)}
3. R3 = {(4, 5)}
4. R4 = {(5, 6), (6, 7)}

Correct Answer: R1 = {(1, 2), (1, 3)}

Solution:

R1 is not a function because the input 1 maps to two different outputs (2 and 3).