# Math Help - Sets, Equivalence Class/Relations

1. ## Sets, Equivalence Class/Relations

The title of this question may be misleading, but I think this is what the question would fall under. The question is:

Let A=the set of natural numbers. Define a binary relation R on AxA as follows: for all (a,b) and (c,d)EAxA, (a,b)R(c,d) if and only if a+d=c+b

a). list five elements in [(1,1)]
b). list five elements in [(3,1)]

our study group is having trouble with this, and we don't know what the question is asking. This is a practice question for the midterm, so any help on this would be nice.

Thank you,
Scott

2. Originally Posted by scottie.mcdonald
Let A=the set of natural numbers. Define a binary relation R on AxA as follows: for all (a,b) and (c,d)EAxA, (a,b)R(c,d) if and only if a+d=c+b
a). list five elements in [(1,1)]
b). list five elements in [(3,1)]
Here is the b part: $[(3,1)]=(4,2);(5,3);(6,4);(7,5);(8,6)$.
You see that $3+6=1+8$?

3. yup, I see how that works. Thanks for the help

Scott