What's the definition of an equivalence relation R on X? (or even better: for which conditions is a relation an equivalence relation?)
I am not sure how to start, and how to use a+d=b+c
Do I plug numbers between 1 to 10 in there?
Let (a,b) R (c,d) be symmetric
therefore R { (a,b) , (c,d) ,(b,a), (d,c)}
Let (a,b) R (c,d) be reflexive
therefore R {(a,b), (c,d)}
Let (a,b) R (c,d) be transitive
therefore R {(a,b) (b,c) (c,d)}
So the Equivalence relation of (a,b) R (c,d) will be {(a,b) , (c,d) ,(b,a), (d,c) (b,c)}
where shall I use a+d= b+c?
Thank you.