The relation R = {(x, y) : x, y Z and x + y is even} is: [2025]
(4)
R = {(x, y) : x, y Z and x + y is even}
For reflexive : x + x = 2x is even
For symmetric : x + y = y + x is even
For transitive : x + y is even and y + z is even then z + x is also even.
So, the relation is an equivalence.