Q.

Let R be a relation on real numbers given by R={(a,b):3a-3b+7 is an irrational number}. Then R is

1 Reflexive but neither symmetric nor transitive  
2 Reflexive and transitive but not symmetric  
3 Reflexive and symmetric but not transitive  
4 An equivalence relation  

Ans.

(1)

Check for reflexivity:    As 3(a-a)+7=7 which belongs to relation

So relation is reflexive.

Check for symmetric

Take a=73, b=0 Now (a,b)∈R but (b,a)∉R

As 3(b-a)+7=0 which is rational so relation is not symmetric

Check for Transitivity,    Take (a,b) as (73,1) & (b,c) as (1,273)

So now (a,b)∈R & (b,c)∈R but (a,c)∉R,

Which means relation is not transitive