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NCERT Solutions for class 12 Maths | Chapter 1 - Relations and Functions

Questions
1 Let E = {1, 2, 3, 4} and F = {1, 2} Then, the number of onto functions from E to F is
A 14
B 16
C 12
D 8

Answer:14
2 Let R be a relation on the set N of natural numbers denoted by nRm ⇔ n is a factor of m (i.e. n | m). Then, R is
A Reflexive and symmetric
B Transitive and symmetric
C Equivalence
D Reflexive, transitive but not symmetric

Answer:Reflexive, transitive but not symmetric
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3 The relation R is defined on the set of natural numbers as {(a, b): a = 2b}. Then, R-1 is given by
A {(2, 1), (4, 2), (6, 3),….}
B {(1, 2), (2, 4), (3, 6),….}
C R-1 is not defined
D None of these

Answer:{(1, 2), (2, 4), (3, 6),….}
4 Let f: R Relations and functions then
A f-1(x) = f(x)
B f-1(x) = -f(x)
C (f o f)x = -x
D f-1(x) = 1/19 f(x)

Answer:f-1(x) = f(x)
5 Let P = {(x, y) | x² + y² = 1, x, y ∈ R]. Then, P is
A Reflexive
B Symmetric
C Transitive
D Anti-symmetric

Answer:Symmetric
6 Let R be a relation on the set N be defined by {(x, y) | x, y ∈ N, 2x + y = 41}. Then R is
A Reflexive
B Symmetric
C Transitive
D None of these

Answer:None of these
7 If f(x) + 2f (1 – x) = x² + 2 ∀ x ∈ R, then f(x) =
A x² – 2
B 1
C 1/3 (x – 2)²
D None of these

Answer:1/3 (x – 2)²
8 Let function R → R is defined as f(x) = 2x³ – 1, then ‘f’ is
A 2x³ + 1
B (2x)³ + 1
C (1 – 2x)³
D 1/3

Answer:1/3
9 The domain of sin-1 (log (x/3)] is. .
A [1, 9]
B [-1, 9]
C [-9, 1]
D [-9, -1]

Answer:[1, 9]
10 Let T be the set of all triangles in the Euclidean plane, and let a relation R on T be defined as aRb if a congruent to b ∀ a, b ∈ T. Then R is
A reflexive but-not transitive
B transitive but not symmetric
C equivalence
D None of these

Answer:equivalence
11 Let us define a relation R in R as aRb if a ≥ b. Then R is
A an equivalence relation
B reflexive, transitive but not symmetric
C neither transitive nor reflexive but symmetric
D symmetric, transitive but not reflexive

Answer:reflexive, transitive but not symmetric
12 If the set A contains 5 elements and the set B contains 6 elements, then the number of one-one and onto mappings from A to B is
A 720
B 120
C 0
D None of these

Answer:0
13 Which of the following functions from Z into Z are bijective?
A f(x) = x³
B f(x) = x + 2
C f(x) = 2x + 1
D f{x) = x² + 1

Answer:f(x) = x + 2
14 For real numbers x and y, we write xRy ⇔ x – y + √2 is an irrational number. Then, the relational R is
A Reflexive
B Symmetric
C Transitive
D None of these

Answer:Reflexive
15 Let R be an equivalence relation on a finite set A having n elements. Then, the number of ordered pairs in R is
A Less than n
B Greater than or equal to n
C Less than or equal to n
D None of these

Answer:Greater than or equal to n
16 The relation R = {(1,1), (2, 2), (3, 3), (1, 2), (2, 3), (1, 3)} on set A = {1, 2, 3} is
A Reflexive but not symmetric
B Reflexive but not transitive
C Symmetric and transitive
D Neither symmetric nor transitive

Answer:Reflexive but not symmetric
17 Let f : R → R be given by f (,v) = tan x. Then f-1(1) is
A π/4
B
C does not exist
D None of these

Answer:Relations and Function
18 Let f: R → R be defined by

Relations and Functions

then f(- 1) + f (2) + f (4) is

A 9
B 14
C 5
D None of these

Answer:9
19 Let f : R → R be defined by f (x) = 1/x ∀ x ∈ R. Then f is
A one-one
B onto
C bijective
D f is not defined

Answer:f is not defined
20 What type of a relation is R = {(1, 3), (4, 2), (2, 4), (2, 3), (3, 1)} on the set A – {1, 2, 3, 4}
A Reflexive
B Transitive
C Symmetric
D None of these

Answer:None of these

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