Question

The following relations from a domain X to a codomain Y are functions: true (T) or false (F)?

Answer 1

Q1. { (1,a), (2,a), (3,c), (4,b) } ⊆ X x Y, where X = {1,2,3,4} and Y =
{a,b,c,d}

Q2. { (1,3), (2,1), (1,2), (3,1) } ⊆ X x Y, where X = Y = {1,2,3 }.

Answer 2

A function should map one element from X to ONLY ONE element from Y.
In Q2, however, you have (1,2) and (1,3)
Meaning 1 is mapped to both 2 and 3.

Answer 3

oh ok i get that so because 1 is mapped to 2 & 3 it cannot be a function ? thanks for your help

Answer 4

That's right :)

Answer 5

cheers !!