1). [ (6,1), (6,2), (6,3) ] 2). [ (0,5), (5,-1), (5,9) ] 3). [ (1,-6), (3,-5), (1,0) ] 4). [ (0,8), (1,7), (2,6) ]. Which of the following relations is a function?

Again, look for repeated entries in the domain. If present, the relation cannot be a function. 1 maps 6 to 1, 2, and 3; 2 maps 5 to - 1 and 9; 3 maps 1 to - 6 and 0; and only 4 has no double mapping. Therefore 4 is a function and the answer.