Given relation R:(a,b)R(c,d)
And ad−bc=5kwhere k∈Z
Now, for reflexive R:(a,b)R(a,b)
⇒ab−ba=0 which is divisible by 5
So, the relation is reflexive,
Now, for symmetric R:(c,d)R(a,b)
⇒ bc−ad=−5k which is divisible by 5
So, the relation is symmetric,
Now for transitive relation, R:(a,b)R(c,d)R(e,f)
Taking example (a,b)≡(1,2),(c,d)≡(10,10),(e,f)≡(4,4)
Now, ad−bc=10−20=−10
cf−ed=40−40=0
But af−be=8−4=4 which is not divisible by 5,
Hence, the relation is reflexive, symmetric but not transitive.