Let A = { 1 , 2 , 3 , 4 , 5 } and R be a relation defined by R = { ( x , y ) : x , y ∈ A , x + y = 5 } . Then, R is

neither reflexive nor transitive

reflexive and symmetric but not transitive

neither reflexive nor symmetric but transitive

Let R be the real line. Consider the following subsets of the plane R × R S = { x , y : y = x + 1 and 0 < x < 2 } T = { x , y : x - y is an integer} Which of the following is true?

T is an equivalence relation on R but S is not

Neither S nor T is an equivalence relation on R

Both S and T are equivalence relations on R

S is an equivalence relations on R and T is not

Let R 1 and R 2 be two relations defined as follows : R 1 = a , b ∈ R 2 : a 2 + b 2 ∈ Q and R 2 = a , b ∈ R 2 : a 2 + b 2 ∉ Q , where Q is the set of all rational numbers, then

Neither R 1 nor R 2 is transitive.

R 1 is transitive but R 2 is not transitive.

R 2 is transitive but R 1 is not transitive.

R 1 and R 2 are both transitive.

Let the relation $\rho$ be defined on R as a ρ b if 1 + a b > 0 . Then

ρ is reflexive and symmetric but not transitive.

ρ is reflexive and transitive but not symmetric

Let N be the set of natural numbers and R be the relation on N × N defined by ( a , b ) R ( c , d ) iff a d = b c for all a , b , c , d ∈ N . Show that R is an equivalence relation.

Given that, N is the set of natural numbers and R be the relation on N × N defined by ( a , b ) R ( c , d ) iff a d = b c for all a , b , c , d ∈ N We know that, a relation R that is reflexive, symmetric and transitive is called an equivalence relation. Reflexive: For any ( a , b ) ∈ N × N a · b = b · a ∴ ( a , b ) R ( a , b ) Thus, R is reflexive Symmetric: For any ( a , b ) , ( c , d ) ∈ N × N ( a , b ) R ( c , d ) ⇒ a · d = b · c ⇒ c · b = d · a ⇒ ( c , d ) R ( a , b ) Thus, R is symmetric Transitive: For any ( a , b ) , ( c , d ) , ( e , f ) , ∈ N × N ( a , b ) R ( c , d ) and ( c , d ) R ( e , f ) ⇒ a · d = b · c and c · f = d · e ⇒ a · d · c · f = b · c · d · e ⇒ a · f = b · e ∴ ( a , b ) R ( e , f ) Thus, R is transitive Therefore, R is an equivalence Relation.

Check whether the relation R defined in the set 1 , 2 , 3 , 4 , 5 , 6 as R = a , b : b = a + 1 is reflexive, symmetric or transitive.

Suppose A = 1 , 2 , 3 , 4 , 5 , 6 . A relation R is defined on set A as: R = { ( a , b ) : b = a + 1 } ∴ R = { ( 1, 2 ) , 2 , 3 , 3 , 4 , 4 , 5 , 5 , 6 } Reflexive Property : A relation R in a set A is said to be reflexive if x , x ∈ R , for every x ∈ A Now, 1 , 1 , 2 , 2 , 3 , 3 , 4 , 4 , 5 , 5 , 6 , 6 ∉ R ∴ R is not reflexive. Symmetric Property : A relation R in a set A is said to be symmetric if x , y ∈ R implies that y , x ∈ R for all x , y ∈ A . Now it can be observed that 1 , 2 ∈ R , but 2 , 1 ∉ R . Hence , R is not symmetric. Transitive Property : A relation R in a set A is said to be transitive if x , y ∈ R and y , z ∈ R implies that x , z ∈ R for all x , y , z ∈ A . Now, 1 , 2 , 2 , 3 ∈ R but, ( 1 , 3 ) ∉ R ∴ R is not transitive. Hence, R is neither reflexive, nor symmetric, nor transitive.

Show that the relation R on R is defined as R = { ( a , b ) : a ≤ b } , is reflexive and transitive but not symmetric.

Given, R = a , b : a ≤ b , a , b ∈ R For the relation R to be reflexive: If the relation R is reflexive, then a , a ∈ R i.e. a ≤ a , which is always true for all the values of a , a ∈ R So, the given relation R is reflexive. For the relation R to be symmetric: If a , b ∈ R then b , a ∈ R i.e. if a ≤ b then b ≤ a , which is not possible for all the values of a , b ∈ R . For example: if a = 2 and b = 5 Here, a < b but b > a So, the given relation R is not symmetric. For the relation R to be transitive: If a , b ∈ R and b , c ∈ R then a , c ∈ R i.e.,if a ≤ b and b ≤ c then a ≤ c , which is true for all the values of a , b , c ∈ R . For example: if a = 2 , b = 3 and c = 4 Here, a < b < c So, the given relation is transitive. Hence, the given relation R is reflexive and transitive but not symmetric.

Let R be the real line. Consider the following subsets of the plane R × R S = { ( x , y ) ∣ y = x + 1 , 0 < x < 2 } T = { ( x , y ) ∣ x - y is an integer } . Which one of the following is true?

T is an equivalence relation on R but S is not

Neither S nor T is an equivalence relation on R

Both S and T are equivalence relation on R

S is an equivalence relation on R and T is not

MEDIUM

Earn 100

Let $R$ be a relation defined on $ℕ$ as a $R$ b is $2 a + 3 b$ is a multiple of $5, a, b \in ℕ$ . Then $R$ is

Important Questions on Relations and Functions

EASY

Mathematics>Algebra>Relations and Functions>Types of Relations

Let

A = {1, 2, 3, 4, 5}

and

R

be a relation defined by

R = {(x, y) : x, y \in A, x + y = 5}

. Then,

R

MEDIUM

Mathematics>Algebra>Relations and Functions>Types of Relations

Let

R

be the real line. Consider the following subsets of the plane

R \times R

S = {(x, y) : y = x + 1

and

0 < x < 2}

T = {(x, y) : x - y

is an integer}

Which of the following is true?

HARD

Mathematics>Algebra>Relations and Functions>Types of Relations

Let

R_{1}

and

R_{2}

be two relations defined as follows :

$R_{1} = \{(a, b) \in R^{2} : a^{2} + b^{2} \in Q\}$ and $R_{2} = \{(a, b) \in R^{2} : a^{2} + b^{2} \notin Q\}$ , where $Q$ is the set of all rational numbers, then

EASY

Mathematics>Algebra>Relations and Functions>Types of Relations

Let

ρ_{1}

and

ρ_{2}

be two equivalence relations defined on a non-void set

S

. Then

EASY

Mathematics>Algebra>Relations and Functions>Types of Relations

A relation

R

in a set

A

is called _____, if

(a_{1}, a_{2}) \in R

implies

(a_{2}, a_{1}) \in R

, for all

a_{1}, a_{2} \in A

MEDIUM

Mathematics>Algebra>Relations and Functions>Types of Relations

Let the relation $\rho$ be defined on

R

a ρ b

1 + a b > 0 .

Then

EASY

Mathematics>Algebra>Relations and Functions>Types of Relations

Let

P

be the relation defined on the set of all real numbers such that

P = \{(a, b) : \sec^{2} a - \tan^{2} b = 1\}

. Then,

P

EASY

Mathematics>Algebra>Relations and Functions>Types of Relations

A = \{1, 2, 3, 4\}

then which one of the following is reflexive?

HARD

Mathematics>Algebra>Relations and Functions>Types of Relations

Let

N

be the set of natural numbers and

R

be the relation on

N \times N

defined by

(a, b) R (c, d) iff a d = b c

for all

a, b, c, d \in N

. Show that

R

is an equivalence relation.

EASY

Mathematics>Algebra>Relations and Functions>Types of Relations

Check whether the relation

R

defined in the set

\{1, 2, 3, 4, 5, 6\}

R = \{(a, b) : b = a + 1\}

is reflexive, symmetric or transitive.

HARD

Mathematics>Algebra>Relations and Functions>Types of Relations

Let

R

and

S

be any two equivalence relations on a set

X

. Then which of the following is incorrect statement

MEDIUM

Mathematics>Algebra>Relations and Functions>Types of Relations

Show that the relation

R

R

is defined as

R = {(a, b) : a \leq b}

, is reflexive and transitive but not symmetric.

MEDIUM

Mathematics>Algebra>Relations and Functions>Types of Relations

Let

A = \{2, 3, 4, 5, \dots ., 16, 17, 18\} .

Let

\approx

be the equivalence relation on

A \times A

cartesian product of

A

and

A

, defined by

(a, b) \approx (c, d)

a d = b c,

then the number of ordered pairs of the equivalence class of

(3, 2)

MEDIUM

Mathematics>Algebra>Relations and Functions>Types of Relations

If a relation

R

on the set

\{1, 2, 3\}

be defined by

R = \{(1, 1)\}

, then

R

EASY

Mathematics>Algebra>Relations and Functions>Types of Relations

Let $R$ be the real line. Consider the following subsets of the plane $R \times R$

$S = {(x, y) ∣ y = x + 1, 0 < x < 2}$

$T = {(x, y) ∣ x - y$ is an integer $} .$ Which one of the following is true?

HARD

Mathematics>Algebra>Relations and Functions>Types of Relations

Define a relation $R$ over a class of $n \times n$ real matrices $A$ and $B$ as " $A R B$ iff there exists a non-singular matrix $P$ such that $P A P^{- 1} = B$ ". Then which of the following is true ?

EASY

Mathematics>Algebra>Relations and Functions>Types of Relations

Let

R = {(P, Q) | P

and

Q

are at the same distance from the origin

}

be a relation, then the equivalence class of

(1, - 1)

is the set

MEDIUM

Mathematics>Algebra>Relations and Functions>Types of Relations

Let

R

be a relation on the set of all natural numbers given by

a R b \Leftrightarrow a

divides

b^{2} .

Which of the following properties does

R

satisfy?

I .

Reflexivity

I I .

Symmetry

I I I .

Transitivity

HARD

Mathematics>Algebra>Relations and Functions>Types of Relations

Let

A = {x \in Z : 0 \leq x \leq 12}

. Show that

R = {(a, b) : a, b \in A, | a - b | is divisible by 4}

is an equivalence relation. Find the set of all elements related to

1

. Also write the equivalence class

[2]

EASY

Mathematics>Algebra>Relations and Functions>Types of Relations

Consider the non-empty set consisting of children in a family and a relation

R

defined as

a R b

a

is brother of

b

. Then

R

Let R be a relation defined on ℕ as a R b is 2a+3b is a multiple of 5,a,b∈ℕ. Then R is

Important Questions on Relations and Functions

Learn and Prepare for any exam you want !

Let $R$ be a relation defined on $ℕ$ as a $R$ b is $2 a + 3 b$ is a multiple of $5, a, b \in ℕ$ . Then $R$ is