1.

Let `f:X->Y` be a function. Define a relation `R` in `X` given by `R={(a,b):f(a)=f(b)}.` Examine whether `R` is an equivalence relation or not.

Answer» Here R satisfies the following properties :
(i) Reflexivity
Let `a in X.` Then
`f(a) =f(a) rArr (a, a) in R`
`:.` R is reflexive .
(ii) Symmetry
Let `(a,b ) in R` Then
`(a,b) in R rArr f(a) =f(b) rArr f(b) =f(a) rArr (b,a) in R`
`:.` R is symmetric.
(iii) Transitivity
Let `(a,b) in R " and " (b,c) in R .` Then
`(a,b) in R , (b,c) in R`
`rArr f(a) =f(b) " and " f(b) =f( c)`
`rArr f(a) =f(c )`
`rArr (a,c) in R`
`:.` R is transitive.
Hence R is an equivalence relation .


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