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JEE Main 201815 April
Exam
JEE Main
Year
2018
Date
15 April
Subject
Mathematics
Chapter
Sets and Relations

JEE Main 2018 · 15 April · Mathematics · Sets and Relations

Consider the following two binary relations on the set A = \ a, b,...

Consider the following two binary relations on the set A=A =\left\{a, b, c\right\}: {R}_{1} = {(c,a),(b,b),(a,c),(c,c),(b,c),(a,a)}\left\{\left(c, a\right), \left(b, b\right), \left(a, c\right), \left(c, c\right), \left(b, c\right), \left(a, a\right)\right\} and R2={(a,b),(b,a),(c,c),(c,a),(a,a),(b,b),(a,c)}{R}_{2} = \left\{\left(a, b\right), \left(b, a\right), \left(c, c\right), \left(c, a\right), \left(a, a\right), \left(b, b\right), \left(a, c\right)\right\}, then :

Options

  1. AR2{R}_{2} is symmetric but it is not transitive
  2. Bboth R1{R}_{1} and R2{R}_{2} are not symmetric
  3. Cboth R1{R}_{1} and R2{R}_{2} are transitive
  4. DR1{R}_{1} is not symmetric but it is transitive

Correct answer

A. R2{R}_{2} is symmetric but it is not transitive

Step-by-step solution

Since, (b,c)∈R1( b, c ) \in {R}_{1} but (c,b)∉R1( c, b ) \notin {R}_{1}

Hence, R1{R}_{1} is not symmetric.

In R1:(b,c)∈R1{R}_{1}: \left(b, c\right) \in {R}_{1} and \left(c, a\right) \in {R}_{1}but(b,a)∉R1but \left(b, a\right) \notin {R}_{1}

So, R1{R}_{1} is not transitive.

R2{R}_{2} is symmetric.

In R2:(b,a)∈R2{R}_{2}: \left(b, a\right) \in {R}_{2} and \left(a, c\right) \in {R}_{1}but(b,c)∉R2but \left(b, c\right) \notin {R}_{2}

So, R2{R}_{2} is not transitive.

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