Determine which of these relations are symmetric
1) x~y if and only if x-y is positive
2) x~y if and only if xy >= 0
3) x~y if and only if x+2y is positive
4) x~y if and only if x+y is positive
5) x~y if and only if x+y is odd
I thought all but 1) but this was wrong.
The only one I...