# Ordered pairs in a relation

• Apr 26th 2010, 07:18 PM
tigergirl
Ordered pairs in a relation
Let A = {2,4,5,6,12,18} and define the relation PD on A by m PD n iff m is a proper divisor of n. List the ordered pairs in this relation.

I know that this means m / n and m can not be equal to n. What I'm know understanding is how to come up with the ordered pairs? Can anyone help
• Apr 27th 2010, 12:45 AM
kompik
Quote:

Originally Posted by tigergirl
Let A = {2,4,5,6,12,18} and define the relation PD on A by m PD n iff m is a proper divisor of n. List the ordered pairs in this relation.

I know that this means m / n and m can not be equal to n. What I'm know understanding is how to come up with the ordered pairs? Can anyone help

You simply try all possibilities, for instance 2|4, so the ordered pair (2,4) belongs to PD, but de pairs (4,2) and (2,5) do not.
If I have not overlooked something, you should get these pairs (but try to do this on your own first, to see whether you really understand it).
PD={(2,4),(2,6),(2,12),(2,18),(4,12),(6,12),(6,18) }.