Q.

The relation R = {(x, y) : x, y  Z and x + y is even} is:          [2025]

1 reflexive and transitive but not symmetric.  
2 reflexive and symmetric but not transitive.  
3 symmetric and transitive but not reflexive.  
4 an equivalence relation.  

Ans.

(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.