# Answer to Question #23581 in Abstract Algebra for Paras

Question #23581

A relation R is defined on the set of integers as xRy iff (x+y) is even. which of the following statement is true ?

a) R is not an equivalence relation

b) R is an equivalence relation having one equivalence class

c) R is an equivalence relation having two equivalence class

d) R is an equivalence relation having three equivalence class

a) R is not an equivalence relation

b) R is an equivalence relation having one equivalence class

c) R is an equivalence relation having two equivalence class

d) R is an equivalence relation having three equivalence class

Expert's answer

a) is false, since xRy meansthat x,y are either both odd either both even. So, xRx as x+x=2x - even,

xRy and yRx as x+y=y+x

xRy and yRz implies xRz as in this case all x,y,z are either odd either even.

b) false

c) true . All integers can be divided into 2 groups: even numbers and odd. Theninside any these groups all their elements are equivalent.

d) false

xRy and yRx as x+y=y+x

xRy and yRz implies xRz as in this case all x,y,z are either odd either even.

b) false

c) true . All integers can be divided into 2 groups: even numbers and odd. Theninside any these groups all their elements are equivalent.

d) false

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