BoardMaths

Relations and Functions

19 Board Maths previous year questions on Relations and Functions — options free on every question; 2 include the answer & explanation free, the rest unlock with PYQ Pass.

Q1 FREE PREVIEW
PYQ

A function \(f: R^{+} \rightarrow R\) (where \(R^{+}\) is the set of all non-negative real numbers) defined by \(f(x)=4 x+3\) is :

a

one-one but not onto

b

onto but not one-one

c

both one-one and onto

d

neither one-one nor onto

✓ Correct answer: a)

one-one but not onto

Explanation

One-One:

Let \(f\left({x}_{1}\right)=f\left({x}_{2}\right)\).

\(4{x}_{1}+3=4{x}_{2}+3\)

\({x}_{1}={x}_{2}\)

Onto:

\(y=4x+3\)

\(x=\frac{y-3}{4}\)

\(x\in [0,\infty )\Rightarrow y\geq 3\)

Range \(=[3,\infty )\neq R\)

Q2 FREE PREVIEW
PYQ

Let the relation \(R\) on the set \(\text{M}=\left\{1,2,3,\ldots ,16\right\}\) be given by \(\text{R}=\left\{\left(x,y\right):4y=5x−3,x,y\in \text{M}\right\}\).

Then the minimum number of elements required to be added in \(R,\) in order to make the relation symmetric, is equal to

[JEE Main 2026, 22 Jan (Shift 1)]

a

3

b

2

c

1

d

4

✓ Correct answer: b)

2

Explanation

Given, \(\text{R}=\left\{\left(x,y\right):4y=5x−3,x,y\in \text{M}\right\}\) and \(\text{M}=\left\{1,2,3,\ldots ,16\right\}\)

\(R=\left\{\left(3,3\right),\left(7,8\right),\left(11,13\right)\right\}\)

To make it symmetric \((8,7),(13,11)\) must be added.

Q3
PYQ

A function \(\mathrm{f}:\mathrm{ℝ}\to \mathrm{ℝ}\) defined as \(\mathrm{f}(x)={x}^{2}-4x+5\) is :

a

injective but not surjective.

b

surjective but not injective.

c

both injective and surjective.

d

neither injective nor surjective.

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Q4
PYQ

The sum of absolute maximum and absolute minimum values of the function \(f(x)=\left|2 x^2+3 x-2\right|+\sin x \cos x\) in the interval \([0,1]\) is:

[JEE Main 2022, 24 Jun (Shift 1)]

a

\(3+\frac{\sin \left(1\right){\cos }^{2}\left(\frac{1}{2}\right)}{2}\)

b

\(3+\frac{1}{2}\left(1+2\cos \left(1\right)\right)\sin \left(1\right)\)

c

\(5+\frac{1}{2}\left(\sin \left(1\right)+\sin \left(2\right)\right)\)

d

\(2+\sin \left(\frac{1}{2}\right)\cos \left(\frac{1}{2}\right)\)

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Q5
PYQ

Let \(f\text{ }:\text{ }{R}_{+}\text{ }\to \text{ }\left[5,\text{ }\infty \right)\) be defined as \(f\left(x\right)=9{x}^{2}+6x-5,\) where \({R}_{+}\) is the set of all non-negative real numbers. Then, \(f\) is

a

one-one

b

onto

c

bijective

d

neither one-one nor onto

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Q6
PYQ

Let \(f: R^{+} \rightarrow[-5, \infty)\) be defined as \(f(x)=9 x^2+6 x-5\), where \(R^{+}\) is the set of all non-negative real numbers. Then, \(f\) is :

a

one-one

b

onto

c

bijective

d

neither one-one nor onto

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Q7
PYQ

A function \(\mathrm{f}:\mathrm{ℝ}\to \mathrm{ℝ}\) defined as \(\mathrm{f}(x)={x}^{2}-4x+5\) is :

a

injective but not surjective.

b

surjective but not injective.

c

both injective and surjective.

d

neither injective nor surjective.

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Q8
PYQ

\(\begin{aligned}& A=\{1,2,3, \ldots, 10\}, \\& B=\left\{\frac{m}{n}, n>m, m, n \in A, \operatorname{gcd}(m \cdot n)=1\right\}\end{aligned}\)
Then no. of elements in \(\mathrm{B}=\) ? (22 Jan, Shift I, Memory Based)

a

31

b

33

c

29

d

28

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Q9
PYQ

A function \(f:{R}_{+}\to R\) where \({R}_{+}\) is the set of all non-negative real numbers) defined by \(f\left(x\right)=4x+3\) is:

a

one-one but not onto

b

onto but not one-one

c

both one-one and onto

d

neither one-one nor onto

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Q10
PYQ

If \(f:\mathrm{R}\to \mathrm{R}\), is given by \(f\left(x\right)={\left(3-{x}^{3}\right)}^{\frac{1}{3}}\), then \(f∘f\left(x\right)\) is equal to :

a

\({x}^{\frac{1}{3}}\)

b

\({x}^{3}\)

c

\(x\)

d

\(\left(3-{x}^{3}\right)\)

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Q11
PYQ

(i) If \(f:R\to R\) be defined as \(f(x)={x}^{2}\). then

a

f is one-one onto

b

f is many one onto

c

f is one-one but not onto

d

f is neither one-one nor onto

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Q12
PYQ

Let R be the relation in the set N given by \(R={(a,b):a=b-2,b>6}\). Choose the correct answer from the following

[PYQ 2024, 2023, 2022]

a

\((6,8)\in R\)

b

\((2,4)\in R\)

c

\((3,8)\in R\)

d

\((8,7)\in R\)

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Q13
PYQ

If R be the relation in the set N given by \(R={(a,b):a=b-2,b>6}\), then

a

\((2,4)\in R\)

b

\((3,8)\in R\)

c

\((6,8)\in R\)

d

\((8,7)\in R\)

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Q14
PYQ

\(\text{ Let }A={a,b,c}\text{ and }R={(a,a),(a,b)(b,a)}\text{ then }R\text{ is }\)

a

reflexive and symmetric but not transitive

b

reflexive and transitive but not symmetric

c

symmetric and transitive but not reflexive

d

an equivalence relation

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Q15
PYQ

In the function \(f:R\to R\), given by \(f(x)=5x\)

a

f is one-one onto

b

f is many-one onto

c

f is one-one but not onto

d

f is neither one-one nor onto

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Q16
PYQ

\(WhattypeofrelationisR={(a,b),(b,c),(b,a),(c,b)onthesetA={a,b,c}?\)

a

Reflexive

b

Symmetric

c

Transitive

d

None of these

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Q17
PYQ

Let \([x]\) denote the greatest integer \(\leq x\), where \(x \in R\). If the domain of the real valued function \(f\left(x\right)=\sqrt{\frac{|[x]|-2}{|[x]|-3}}\) is \((-\infty, a) \cup[b, c) \cup[4, \infty), a

a

\(-3\)

b

\(8\)

c

\(-2\)

d

\(1\)

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Q18
PYQ

if \(\text{ }f:R\to R\) be such that \(\text{ }f(x)=5x+4\)then,\(\text{ }{f}^{-1}(x)=\)

a

\(\frac{\left(x-4\right)}{5}\)

b

\(\frac{\left(4-x\right)}{5}\)

c

\(\frac{(x-5)}{4}\)

d

None of these

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Q19
PYQ

If \(f:\mathrm{R}\to \mathrm{R},f(x)=\sin xandg:\mathrm{R}\to \mathrm{R},g(x)={x}^{2}\)

then \((f∘g)(x)\) is equal to:

a

\(\sin {x}^{2}\)

b

\(\sin x\)

c

\({\sin }^{2}{x}^{2}\)

d

\({\sin }^{2}x\)

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