1.

Show that the relation R in the set A of all the books in a library of a college, given by R = {(x, y) : x and y have same number of pages} is an equivalence relation.

Answer» Set `A` is the set of all books in the library of a college.
`R = {x, y): x` and `y` have the same number of pages}.
Now, R is reflexive since `(x, x) in R` as `x` and `x` has the same number of pages.
Let `(x, y) in R => x` and `y` have the same number of pages.
`=> y` and `x` have the same number of pages.
`=> (y, x) in R`.
`:. R` is symmetric.
Now, let `(x, y) in R` and `(y, z) in R`.
`=> x` and `y` and have the same number of pages and `y` and `z` have the same number of pages.
It means `x` and `z` have the same number of pages.
=> `(x, z) in R`.
`:. R` is transitive.
As `R` is reflexive, summetric and transitive, `R` is an equivalence relation.


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