Q.

Let A be the set of all functions f : Z  Z and R be a relation on A such that R = {(f, g) : f(0) = g(1) and f(1) = g(0)}. Then R is :          [2025]

1 Transitive but neither reflexive nor symmetric.  
2 Symmetric and transitive but not reflexive.  
3 Symmetric but neither reflexive nor transitive.  
4 Reflexive but neither symmetric nor transitive.  

Ans.

(3)

We have, R = {(f, g) : f(0) = g(1) and f(1) = g(0)}

For reflexive: (f, f R

  f(0) = f(1) must hold f

But f(0)  f(1)

Therefore, R is not reflexive.

For symmetric: If (f, g R  (g, f R

Now, g(0) = f(1) and g(1) = f(0), which is true f

  R is symmetric

For transitive : IF (f, g R and (g, h R  (f, h R

Now, (f, g R  f(0) = g(1) and f(1) = g(0)

          (g, h R  g(0) = h(1) and g(1) = h(0)

For (f, h R, we need f(0) = h(1) and f(1) = h(0)

But, f(0) = g(1) = h(0)  h(1) and f(1) = g(0) = h(1)  h(0)

Hence, R is not transitive.