NCERT Exemplar Class 11 Maths Solutions Chapter 2 Relations and Functions

NCERT Exemplar Class 11 Maths Solutions Chapter 2 Relations and Functions

Edited By Ravindra Pindel | Updated on Sep 12, 2022 04:42 PM IST

NCERT Exemplar Class 11 Maths solutions chapter 2 Relations and Functions deals with advanced operations related to sets learned in previous chapter sets. NCERT Exemplar Class 11 Maths chapter 2 solutions help define the link between two elements of different sets in a pair is also known as a relation. This could be understood with an easy example. Let’s say there are two different sets, one is A containing name of students in a class and set B contains the marks obtained by the students of the same class. So to find the result and progress of students, teachers link the marks, and names of the students which are defining a relation between the pairs of elements belonging to different sets.

NCERT Exemplar Class 11 Maths Solutions Chapter 2: Excercise-1.3

Question:1

Let A = \left \{ -1,2,3\right \} and B = \left \{ 1,3\right \}. Determine
I) AXB ii)BXA iii) BXB iv) AXA

Answer:

Given data: A = \left \{ -1,2,3\right \} and B = \left \{ 1,3\right \}.

Now, let’s solve the problems one by one-
i)A \times B = \left \{-1, 2, 3}{ \right \} X \left \{1, 3}{ \right \}= \left \{(-1, 1), (-1, 3), (2, 1), (2, 3), (3, 1), (3, 3) \right \}
ii)B \times A = \left \{1, 3}{ \right \} \times \left \{-1, 2, 3}{ \right \}= \left \{(1, -1), (3, -1), (1, 2), (3, 2), (1, 3), (3, 3)}{ \right \}
iii)B \times B = \left \{1, 3}{ \right \} \times \left \{1, 3}{ \right \} = \left \{(1, 1), (1, 3), (3, 1), (3, 3)}{ \right \}
iv)A \times A = \left \{-1, 2, 3}{ \right \} \times \left \{-1, 2, 3}{ \right \}= \left \{(-1, -1), (-1, 2), (-1, 3), (2,-1), (2, 2), (2, 3), (3, -1), (3, 2), (3, 3)}{ \right \}


Question:2

If P = \left \{ {x : x < 3, x \in N} \right \}, Q = \left \{ {x : x \leq 2, x \in W} \right \}. Find (P \cup Q) \times (P \cap Q), where W is the set of whole numbers.
Answer:

Given data:

P = \left \{x:x < 3, x \in N}{ \right \} \rightarrow P = \left \{1, 2}{ \right \}

Q = \left \{x:x \leq 2, x \in W}{ \right \} \rightarrow Q =\left \{ 0,1,2 \right \}

Now, (P \cup Q) = \left \{0, 1, 2}{ \right \} \: \: and\: \: (P \cap Q) = \left \{1, 2}{ \right \}

Thus, (P \cup Q) \times (P \cap Q) =\left \{ {0, 1, 2} \right \} \times \left \{ {1, 2} \right \} = \left \{ {(0, 1), (0, 2), (1, 1), (1, 2), (2, 1), (2, 2)} \right \}


Question:3

If A = \left \{ {x : x \in W, x < 2} \right \},B = \left \{ {x : x \in N, 1 < x < 5} \right \}, C = \{ 3, 5\} find

I)A \times (B \cap C) (ii) A \times (B \cup C)

Answer:

Given data:

C = \left \{3, 5\right \}

Now, we can find,

(B \cap C) = \left \{3\right \} &

(B \cup C) = \left \{2, 3, 4, 5\right \}
i)A \times (B \cap C) = \left \{0, 1\right \} \times \left \{3\right \} = \left \{(0, 3), (1, 3)\right \}
ii)A \times (B \cup C) = \left \{0, 1\right \} \times \left \{2, 3, 4, 5\right \} = \left \{(0, 2), (0, 3), (0, 4), (0, 5), (1, 2), (1, 3), (1, 4), (1, 5)\right \}


Question:4

In each of the following cases, find a and b.
(i) (2a + b, a - b) = (8, 3)

(ii) (a/4 , a - 2b) = (0, 6 + b)

Answer:

i) Given data:
(2a + b, a - b) = (8, 3)

If & only if the corresponding coordinates are equal the two ordered pairs will be equal.

Thus, 2a + b = 8 …… (i)

& a - b = 3 ……. (ii)

From (i) & (ii), we get,

A = 11/3 & b = 2/3

ii) Given data:

(a/4, a - 2b) = (0, 6 + b)

If & only if the corresponding coordinates are equal the two ordered pairs will be equal.

Thus, a/4 = 0 \rightarrow a = 0

& a - 2b = 6 + b \rightarrow a � 3b = 6

0 - 3b = 6

b = -2

Thus, a = 0 & b = -2

Question:5

Given A = \left \{1, 2, 3, 4, 5\right \}, S = \left \{(x, y) : x \in A, y \in A\right \}. Find the ordered pairs which satisfy the conditions given below:
(i) x + y = 5
(ii) x + y < 5
(iii) x + y > 8

Answer:

Given data:

A = \left \{1, 2, 3, 4, 5\right \} &

S = \left \{(x, y) : x \in A, y \in A\right \}

Now,

  1. The ordered pairs that satisfying the given condition,x + y = 5 are, (1,4), (4,1), (2,3) \& (3,2).

  2. The ordered pairs that satisfying the given condition, x + y < 5 are, (1,1), (1,2), (2,1), (1,3), (2,2), (3,1).

  3. The ordered pairs that satisfying the given condition, x + y > 8 are, (4,5), (5,4), (5,5).

Question:6

GivenR = \left \{(x, y) : x, y \in W, x^2 + y^2 = 25\right \}. Find the domain and Range of R.

Answer:

Given data:

R = \left \{(x,y) : x, y \in W, x^2 + y^2 = 25\right \}

(0,5), (3,4), (5,0) \& (4,3), are the ordered pairs satisfying the condition x^2 + y^2 = 25.

Therefore, here,

Domain = \left \{0,3,4,5\right \} &

Range = \left \{0,3,4,5\right \}

Question:7

If R1 = \left \{(x, y) | y = 2x + 7, where\: \: x \in R \: \: and - 5 \leq x \leq 5\right \} is a relation. Then find the domain and Range of R1.

Answer:

Given data: R1 = \left \{(x, y) / y = 2x + 7 \: \: where\: \: x \in R \and -5 \leq x \leq 5\right \}

Thus, domain of R1 will be \left \{x: -5 \leq x \leq 5 = [-5,5] \right \}

Domain = \left \{-5,-4,-3,-2,-1,0,1,2,3,4,5\right \}

& y = 2x + 7

Thus, the values of y will be-

\left \{-3,-1,1,3,5,7,9,11,13,15,17\right \}

Thus, domain of R_1 = [-5,5]

& range of R_1 = [-3,17]

Question:8

If R_2 = \left \{(x, y) | \: \: x \: \: and \: \: y \: \: are \: \: integers \: \: and\: \: x^2 + y^2 = 64\right \} is a relation. Then find R_2.

Answer:

Given data:x^2 + y^ 2 = 64, where x & y \in Z

Thus, it is clear that 64 is the sum of the squares of 2 integers

Thus, for, x=0

Y will be = \pm8 & vice-versa.

Therefore, R_2 = \left \{(0,8),(0,-8),(8,0),(-8,0)\right \}

Question:9

If R3 = \left \{(x, |x|) |x \: \: is\: \: a\: \: real\: \: number\right \}is a relation. Then find domain and range of R3.

Answer:

Given data: R_3 = \left \{(x,|x|\right \} where x is a real no.

Thus, domain of R3 will be equal to that of R & its range will be

R_3 = (o, \infty) ... (since,\left|x\right| = R_+]

Question:10

Is the given relation a function? Give reasons for your answer.

(i) h = \left \{(4, 6), (3, 9), (- 11, 6), (3, 11)\right \}

(ii) f = \left \{(x, x) | x \: \: is \: \: a \: \: real\: \: number\right \}

(iii) g = n, (1/n) |n \: \: is\: \: a\: \: positive\: \: integer

(iv)s = \left \{(n, n2) | n \: \: is\: \: a\: \: positive\: \: integer\right \}

(v) t = \left \{(x, 3) | x \: \: is \: \: a \: \: real\: \: number\right \}.

Answer:

(i) Given data: h = \left \{(4,6),(3,9),(-11,6),(3,11)\right \}

‘h’ is not a function since there are two images- 9 & 11 for the relation 3.

(ii) f = \left \{(x,x)/ x \: \: is\: \: a\: \: real\: \: no.\right \}

Here, f is a function because every element of the domain has a unique image.

(iii) g = \left \{(n, 1/n)/ n \: \: is\: \: a\: \: positive\: \: integer\right \}

‘g’ is a function because there is a unique image, ‘1/n’ for every element in the domain.

(iv)
S = \left \{(n, n2)/ n \: \: is\: \: a\: \: positive\: \: integer.\right \}

‘S’ is a function since square of any integer is a unique no. & thus, for every element in the domain there is a unique image.

(V) T = \left \{(x,3)/ x \: \: is\: \: a\: \: real\: \: number\right \}

Here ‘t’ is a constant function, since we can observe that there is a constant no. 3 for every real element in the domain.

Question:11

If f and g are real functions defined by f (x) = x^2 + 7 and g (x) = 3x + 5, find each of the following
(a) f (3) + g (- 5)

(b) f(1/2) \times g(14)

(c) f (- 2) + g (- 1)

(d) f (t) - f (- 2)

(e) (f(t) - f(5))/ (t - 5), if \: \: t \neq 5

Answer:

Given data: f(x) = x^2 + 7 & g(x) = 3x + 5

  1. f(3) + g(-5) = [(3)^2 + 7] + [3(-5) + 5]

= 16 - 10

= 6

  1. f( 1/2 ) \times g(14) = [(1/2)^2 + 7] \times [3 \times 14 + 5]

= 29/4 \times 47

= 1363/4

  1. f(-2) + g(-1) = [(-2)^2 + 7] + [(-1) + 5]

= 11 + 2 = 13

  1. f(t) - f(-2) = (t^2 + 7) - [(-2)^2 + 7]

= t^2 - 4

  1. f(t) - f(5)/ t - 5, (t is not equal to 5) = (t^2 + 7) - (5^2 + 7)/ t - 5

=( t^2 + 7 - 32)/t - 5

= (t^2 - 25)/ (t - 5)

=(t - 5) (t + 5)/(t - 5)

= t + 5

Question:12

Let f and g be real functions defined byf (x) = 2x + 1and g (x) = 4x - 7.
(a) For what real numbers x, f (x) = g (x)?

(b) For what real numbers x, f (x) < g (x)?

Answer:

Given data: f(x) = 2x + 1& g(x) = 4x -7

i) Now, for, f(x) = g(x),

2x + 1 = 4x - 7

-2x = -8

Thus, x = 4, viz, the required real no.

ii) For, f(x) < g(x),

2x + 1 < 4x - 7

-2x < -8

Thus, 2x > 8

Thus, x > 4, viz., the required real no.

Question:13

If f and g are two real valued functions defined as f (x) = 2x + 1, g (x) = x^2 + 1, then find.

(i) f + g (ii) f - g (iii) fg (iv)f/g

Answer:

Given data: f (x) = 2x + 1 & g (x) = x^2 + 1
i) f + g = f(x) + g(x)

= 2x+1+x^2+1

= x^2 + 2x + 2
ii) f- g = f(x) - g(x)

= (2x + 1) - (x^2 + 1)

= 2x - x^2

iii) f.g = f(x).g(x)

= (2x + 1) (x^2 + 1)

= 2x^3 + x^2 + 2x + 1

iv) f/8 = f(x)/g(x)

= 2x + 1/x^2 + 1

Question:14

Express the following functions as set of ordered pairs and determine their range.

f: X \rightarrow R, f (x) = x^3 + 1, where X = \left \{-1, 0, 3, 9, 7\right \}

Answer:

Given data: F: x \rightarrow R, f(x) = x^3 + 1, where, x = \left \{-1,0,3,9,7\right \}

We know that, here, x = \left \{-1,0,3,9,7\right \}

For x = -1,

f(-1)^3 + 1 = 0

For x = 0,

f(0) = (0)^3 + 1 = 1

For x = 3,

f(3) = (3)^3 + 1 = 28

For x = 9,

F(9) = (9)^3 + 1 = 730

For x = 7,

F(7) = (7)^3 + 1 = 344

Thus, (-1,0),(0,1),(3,28),(7,344) \& (9,730) are the ordered pairs &

Range = \left \{0,1,28,344,730\right \}.

Question:15

Find the values of x for which the functions

f (x) = 3x^2 - 1 \: \: and \: \: g (x) = 3 + x are equal.

Answer:

Given data: f (x) = 3x^2 - 1 \: \: and \: \: g (x) = 3 + x

Now, it is given that - f(x) = g(x),

Thus, 3x^2 - 1 = 3 + x

3x^2 - x - 4 = 0

3x^2 - 4x + 3x - 4 = 0

x(3x - 4) + 1(3x - 4) = 0

(3x - 4)(x + 1) = 0

3x - 4 = 0 \: \: or\: \: x + 1= 0

3x = 4 \: \: or\: \: x = -1

x = 4/3

Thus, -1 & 4/3 are the values of x.

Question:16

Is g = \left \{(1, 1), (2, 3), (3, 5), (4, 7)\right \}a function? Justify. If this is described by the relation, g (x) = \alpha x + \beta, then what values should be assigned to \alpha \ and \ \beta ?

Answer:

Given data:

g = \left \{(1,1),(2,3),(3,5),(4,7)\right \}

Here, ‘g’ is a function since every element of the domain has unique image.

g(x) = \alpha x + \beta ... (given)

Now, for (1,1)

g(1) = \alpha (1) + \beta = 1

\alpha + \beta = 1 ....... (i)

& for (2,3),

g(2) = \alpha (2) + \beta = 3

2\alpha + \beta = 3 ........ (ii)

On solving (i) & (ii), we get,

\alpha = 2 \: \: and\: \: \beta = -1.

g(x) = 2x -1

It is satisfying for other values of x hence it is a function.

Question:17

Find the domain of each of the following functions given by

i) f(x) = \frac{1}{\sqrt{1-\cos x}}

ii) f(x) = \frac{1}{\sqrt{x+\left | x \right |}}

iii)f(x) =x\left | x \right |

iv) f(x) =\frac{x^3-x+3}{x^2-1}

v) f(x) =\frac{3x}{2x-8}

Answer:

i) Given data: f(x) = \frac{1}{\sqrt{1-\cos x}}
Now, we know that,
-1 \leq cosx \leq 1
1 \geq -cosx \geq -1
1 + 1 \geq 1 - cos x \geq -1+1
2 \geq 1 - cos x \geq 0
0 \leq 1 - cos x \leq 2
Now, for the real value of the domain,
1 - cos x\neq0,cosx \neq 1
But, x \neq 0\: \: 2n\pi \: \: \forall n \in Z
Thus, domain of f = R - \left \{2n\pi, n \in Z\right \}

ii)Given data: f(x) = \frac{1}{\sqrt{x+\left | x \right |}}
Now, x + \left |x \right | = x+x = 2x ...... if \: \: x \geq0
&x + \left |x \right | = x - x = 0 ...... if \: \: x < 0
Now, x<0 is not defined so far, hence,
The domain = R^+
iii)Given data:f(x) =x\left | x \right |
For all x \in R, f(x) is defined
Thus, domain of f = R.
iv)Given data:f(x) =\frac{x^3-x+3}{x^2-1}
Here, only ifx^2 - 1 \neq 0, f(x) is defined,
(x-1)(x+1) \neq 0,
Thus, x \neq 1
and\: \: x \neq -1
Therefore, domain of f = R - \left \{-1,1\right \}
v)Given data: f(x) =\frac{3x}{2x-8}

F(x) is only defined at 2x - 8 \neq 0, x \neq 4,

Thus, the domain = R - \left \{4\right \}.

Question:18

Find the range of the following functions given by

i) f\left ( x \right )= \frac{3}{2-x^2}

ii)f\left ( x \right )= 1-\left | x-2 \right |

iii) f\left ( x \right )= \left | x-3 \right |

iv) f\left ( x \right )= 1+3\cos 2x

Answer:

i)Given data: f\left ( x \right )= \frac{3}{2-x^2}
Let us consider that, y = f(x)
Thus, y = 3/(2 - x^2)
Thus,
y(2 - x^2) = 3
2y - yx^2 = 3
yx^2 = 2y - 3
x^2 = 2 - 3/y
x is real, if 2y - 3 \geq0 \: \: and\: \: y \geq0
Thus, y \geq 3/2
Therefore,
Range of f = (3/2, \infty)
ii)Given data: f\left ( x \right )= 1-\left | x-2 \right |
Now, we know that,
\left |x-2 \right | = -(x-2) , if x < 2, \: \: and\: \: \left | x-2 \right |= (x-2), if \geq 2
Thus, \left |-x-2 \right | \geq 0
Thus, 1 -\left | x-2 \right | \leq 1
Therefore,
Range off = (-\infty, 1)
iii)Given data: f\left ( x \right )= \left | x-3 \right |

Now, we know that,

\left |x-3 \right | \geq 0

Thus, f(x) = 0
Therefore, range of f = (0,\infty)
iv)Given data: f\left ( x \right )= 1+3\cos 2x

Now, we know that,

-1 \leq cos 2x \leq 1

Thus, -3 \leq 3 cos 2x \leq 3

-3 + 1 \leq 1 + 3 cos 2x \leq 3 + 1

Thus, -2 \leq 1 + 3 cos 3x \leq 4

-2 \leq f(x) \leq 4

Therefore, range of f = [-2, 4].

Question:19

Redefine the function f(x) = |x - 2| + |2 + x|, - 3 \leq x \leq 3
Answer:

Given data: f(x) = |x - 2| + |2 + x|, - 3 \leq x \leq 3

Now, \left |x-2 \right | = (x-2), x \geq 2, since\: \: \left |x-2 \right | = -(x-2), x < 2

Now, \left |2+x \right |= -(2+x), x < -2

\left |2+x \right |= (2 + x), x \geq -2

Now, since

f(x) = x-2+ x-3, -3\leq x\leq 3

f(x)=\left\{\begin{matrix}-\left (x-2 \right )-\left (2+x \right ), -3\leq x\leq -2 \\ -\left (x-2 \right )+\left (2+x \right ),-2\leq x\leq 2 \\ \left (x-2 \right )+\left (2+x \right ),2\leq x\leq 3 \end{matrix}\right.

Thus,

f(x) = \left\{\begin{matrix}-2x,-3\leq x<-2 \\ 4,-2\leq x<2 \\ 2x,2\leq x\leq 3 \end{matrix}\right.

Question:20

If f(x)=\frac{x-1}{x+1}, then show that:

i)f(\frac{1}{x})=-f(x) ii) f(-\frac{1}{x})=\frac{-1}{f(x)}

Answer:

Given data: f(x)=\frac{x-1}{x+1}
i) f(1/x) = \frac{\frac{1}{x}-1}{\frac{1}{x}+1}
= \frac{1-x}{1+x}
= -(x-1)/x+1 = -f(x)
Thus, f(1/x) = -f(x)
ii) f(-1/x) = \frac{\frac{-1}{x}-1}{\frac{-1}{x}+1}
= 1 + x/1 - x
=\frac{ 1}{1 + x/1 - x}
= -1/ f(x)
Thus, f(-1/x) = -1/f(x).

Question:21

Letf(x) = \sqrt{x}\: \: and\: \: g (x) = x be two functions defined in the domain R^+\cup \left \{0\right \}. Find

(i)(f + g) (x)

(ii) (f - g) (x)

(iii) (fg) (x)

(iv) (f/g) (x)

Answer:

Given data: f(x) = \sqrt{x}\: \: and\: \: g (x) = xare the two functions which are defined in the domain R^+ \cup \left \{0\right \}

Now, (i) (f+g)(x) = f(x) + g(x)

=\sqrt{x} + x

ii) (f-g)(x) = f(x) - g(x)

=\sqrt{x} - x

iii)(fg)(x) = f(x).g(x)

= \sqrt{x}.x

= x^{3/2}

iv) (f/g)(x) = f(x)/g(x)

= \sqrt{x}/x

= 1/\sqrt{x}

Question:22

Find the domain and Range of the function f (x) = 1/\sqrt{(x-5)}.
Answer:

Given data: f (x) = 1/\sqrt{(x-5)}

When, x-5>0, i.e., x>5, f(x) is real

Thus, domain = (5, \infty)

Now, in order to find the range, we will put

y = f(x) = 1/\sqrt{x-5}

Thus,\sqrt{x-5 }= 1/y

x-5 = 1/y^2

x = 1/y^2 + 5

Therefore, for x \in (5, \infty), y \in R.

Therefore, range off = R^+

Question:23

If f( x)= y = ax-b/ cx-a then prove that f (y) = x

Answer:

Given data: f( x)= y = ax-b/ cx-a

Now, let us put x = y in f(x),

f(y) = ay-b/cy-a

= \frac{a\frac{\left |ax-b \right |}{\left | cx-a \right |}-b}{c\frac{\left |ax-b \right |}{\left | cx-a \right |}-a}

Thus, f(y) = \frac{a^2x-ab-bcx+ab}{cax-bc-cax+a^2}

= \frac{a^2x-bcx}{a^2-bc}

= \frac{x(a^2^-bc)}{a^2-bc}

=x

Therefore, f(y) = x.

Question:24

Let n(A) = m, and n(B) = n. Then the total number of non-empty relations that can be defined from A to B is
(a) mn
(b) nm- 1
(c) mn - 1
(d) 2mn- 1

Answer:

Given data: n(A) = m & n(B) = n

Thus, n(AxB) = n(A).n(B)

= mn

Thus, 2^{mn-1} is the total no. of relations,
Therefore, opt (d) is correct.

Question:25

If[x]^2 - 5[x] + 6 = 0, where [. ] denote the greatest integer function, then
(a) x \in [3,4]
(b) x\in (2, 3]
(c)x\in [2, 3]
(d) x \in [2, 4)

Answer:

x \in [2,3]Given data: [x]^2 - 5[x] + 6 = 0

Thus, [x]^2 - 3[x]2[x] + 6 = 0

[x]([x]-3) - 2([x]-3) = 0

([x]-3)([x]-2) = 0

Thus,[x] = 2,3

Or we can say that x \in [2,4)

Therefore, opt (d) is the correct option.

Question:26

Range of f\left ( x \right )=\frac{1}{1-2\cos x} is

A.\left [ \frac{1}{3},1 \right ]
B.\left [-1, \frac{1}{3} \right ]
C. \left ( -\infty ,-1 \right ]\cup \left [ -\frac{1}{3},1 \right )
D.\left [ -\frac{1}{3},1 \right ]

Answer:

Given data: f\left ( x \right )=\frac{1}{1-2\cos x}

Now, we know that,

-1 \geq \cos x \geq1

Thus, -1\leq cosx \leq 1

-2 \leq -2cosx \leq 2

\\ -1 \leq 1-2 \cos x<0 \text { or } 0<1-2 \cos x \leq 3 \\\\ -1 \geq \frac{1}{1-2 \cos x}>-\infty \text { or } \infty>\frac{1}{1-2 \cos x} \geq \frac{1}{3} \\\\\ \frac{1}{1-2 \cos x} \in(-\infty,-1] \cup\left[\frac{1}{3}, \infty\right)
Therefore, (c) is the correct option.

Question:27

Let f(x)=\sqrt{(1+x^2 )}, then
A. f (xy) = f (x) . f (y)
B. f (xy) \geq f (x) . f (y)
C. f (xy) \leq f (x) . f (y)
D. None of these

Answer:

Given data: f(x)=\sqrt{(1+x^2 )},
f(xy) = \sqrt{(1+x^2 y^2 )}
f(x).f(y) = \sqrt{(1+x^2 )}. \sqrt{(1+x^2 y^2 )}
=\sqrt{1+x^2+y^2+ x^2 y^2 }
Thus, \sqrt{1+x^2 y^2 } \leq \sqrt{1+x^2+y^2+ x^2 y^2 }

i.e.,f(xy)\leq f(x).f(y)

Thus, (c) is the correct answer.

Question:28

Domain of \sqrt{a^2-x^2 } (a>0) is
A. (- a, a)
B. [- a, a]
C. [0, a]
D. (- a, 0]

Answer:

Let us take,

f(x) = a^2-x^2

& f(x) is defined at a^2-x^2\geq 0

x^2-a^2 \leq 0

x^2\leq a^2

Thus, -a\leq x\leq a

Thus, domain of f(x) will be [-a,a]

Therefore, (b) is the correct answer.

Question:29

Iff(x)= ax+ b, where a and b are integers, f(-1) = -5 and f(3) - 3, then a and b are equal to
(a) a = -3, b =-1
(b) a = 2, b =-3
(c) a = 0, b = 2
(d) a = 2, b = 3

Answer:

Given data: f(x)= ax+ b

Now, f(-1) = a(-1) + b

i.e., -5 = -a +b

Thus, a-b = 5 ......... (i)

Now, f(3) = 3a + b

i.e., 3 = 3a +b

Thus, 3a + b = 3 ..... (ii)

From (i) & (ii), we get,

a = 2 & b = -3

Therefore, (b) is the correct answer.

Question:30

The domain of the function f defined by f(x)=\sqrt{4-x}+\frac{1}{\sqrt{x^2-1}} is equal to
A. (- \infty, - 1) \cup (1, 4]

B. (- \infty, - 1] \cup (1, 4]
C. (- \infty, - 1) \cup [1, 4]
D. (- \infty, - 1) \cup [1, 4)

Answer:

Given data: f(x)=\sqrt{4-x}+\frac{1}{\sqrt{x^2-1}}

Now, we know that,

f(x) is defined when, 4-x\geq0\: \: and \: \: x^2-1>0

Thus, -x\geq-4 \: \: and \: \: (x-1)(x+1)>0

Thus, x\leq 4\: \: and\: \: x<-1/x>1

Thus, the domain of f(x) =(-\infty,-1)\cup(1,4]

Therefore, opt (a) is the correct answer.

Question:31

The domain and range of the real function f defined byf(x) = \frac{4-x}{x-4} is given by


    1. Domain = R, Range = \left \{-1, 1\right \}

    2. Domain = R - \left \{1\right \}, Range = R

    3. Domain = R - \left \{4\right \}, Range = \left \{- 1\right \}

    4. Domain = R - \left \{- 4\right \}, Range = \left \{-1, 1\right \}

Answer:

Given data: y=f(x) = \frac{4-x}{x-4}

We know that, the domain of f(x) = R-\left \{4\right \}

Thus, yx - 4y = 4-x

yx+x = 4y+4

x(y+1) = 4y+4

x = 4(1+y)/1+y

Now, if x is a real no. then,

1+y \neq 0

Thus, y \neq -1

Thus, the range off(x) = R - (-1)

Thus, opt (c) is the correct answer.

Question:32

The domain and range of real function f defined by f (x) =\sqrt{ x-1} is given by


    1. Domain = (1, \infty), Range = (0, \infty)

    2. Domain = [1, \infty), Range = (0, \infty)


    1. Domain = [1, \infty), Range = [0, \infty)

    2. Domain = [1, \infty), Range = [0, \infty)

Answer:

Given data: f (x) =\sqrt{ x-1}

f(x) is defined x-1 \geq 0

& domain of f(x) = [1,\infty)

Now, let y = f(x) =\sqrt{ x-1}

y^2 = x - 1

Thus, x = y^2 + 1

Now, if x is real then y should \in R

Thus, Range of f(x) = [0,\infty)
Hence opt (d) is the correct answer.

Question:33

The domain of the function f given by f(x) = (x^2+2x+1)/(x^2-x-6)
A. R - \left \{3, - 2\right \}
B. R - \left \{-3, 2\right \}
C. R - [3, - 2]
D. R - (3, - 2)

Answer:

Given data: f(x) = (x^2+2x+1)/(x^2-x-6)

Now, f(x) is defined by x^2-x-6=0

Thus, x^2-3x+2x-6\neq0

(x-3)(x+2) \neq 0

Thus,x \neq -2 or 3

Thus domain of f(x) = R-\left \{-2,3\right \}

Hence the correct answer is opt (a).

Question:34

The domain and range of the function f given by f (x) = 2 - \left |x -5 \right | is
A. Domain = R+, Range = ( - \infty, 1]
B. Domain = R, Range = ( - \infty, 2]
C. Domain = R, Range = (- \infty, 2)
D. Domain = R+, Range = (- \infty, 2]

Answer:

Given data: f (x) = 2 - \left |x -5 \right |
& f(x) is defined by x \in R

Thus, its domain is f(x) = R

\left |x-5 \right | \geq 0

-|x-5| \leq 0

2-\left |x-5 \right |\leq 2

Thus, f(x) \leq 2

Thus, range of f(x) =(-\infty,2]

Therefore, opt (b) is the correct answer.

Question:35

The domain for which the functions defined byf (x) = 3x^2 - 1 and g (x) = 3 + xare equal is

A.\left \{ -1,\frac{4}{3} \right \}
B.\left [ -1,\frac{4}{3} \right ]
C.\left ( -1,\frac{4}{3} \right )
D.\left [ -1,\frac{4}{3} \right )

Answer:

Given data: f (x) = 3x^2 - 1 and g (x) = 3 + x

Now, f(x) = g(x)

Thus,

3x^2 - 1 = 3 + x

x(3x-4) + 1(3x-4) = 0

Thus, x+1 = 0 or 3x-4 = 0

Thus, x = -1 or x = 4/3

Thus, its domain is \{ -1, 4/3\}

Therefore, (a) is the correct option.

Question:36

Let f and g be two real functions given by f= \left \{(0, 1), (2,0), (3,.-4), (4,2), (5, 1)\right \}
g= \left \{(1,0), (2,2), (3,-1), (4,4), (5, 3)\right \} then the domain of f \times g is given by________ .

Answer:

Given data: f = \left \{(0,1),(2,0),(3,-4),(4,2),(5,1)\right \} \& g = \left \{(1,0),(2,2),(3,-1),(4,4),(5,3)\right \}

Thus, domain of f is\left \{0,2,3,4,5\right \} & that of g = \left \{1,2,3,4,5\right \}

Now, domain of f.g = \left \{2,3,4,5\right \}

Thus, the filler is\left \{2,3,4,5\right \}.

Question:37

Let f= \left \{(2,4), (5,6), (8, -1), (10, -3)\right \} and g = \left \{(2, 5), (7,1), (8,4), (10,13), (11, 5)\right \} be two real functions. Then match the following:


a

f-g

i

\left \{ \left ( 2,\frac{4}{5} \right ),\left ( 8,\frac{-1}{4} \right ),\left ( 10,\frac{-3}{13} \right ) \right \}

b

f+g

ii

\left \{ \left ( 2,20 \right ),\left ( 8,-4 \right ),\left ( 10,-39 \right ) \right \}

c

fxg

iii

\left \{ \left ( 2,-1 \right ),\left ( 8,-5 \right ),\left ( 10,-16 \right ) \right \}

d

f/g

iv

\left \{ \left ( 2,9 \right ),\left ( 8,3 \right ),\left ( 10,10 \right ) \right \}

Answer:

Given data: f= \left \{(2,4), (5,6), (8, -1), (10, -3)\right \} and g = \left \{(2, 5), (7,1), (8,4), (10,13), (11, 5)\right \}
Domain of f(x)$ is \{2,5,8,10\}, Domain of g(x)$ is \{2,7,8,10,11\}

Now, f-g, f+g, f.g & f/g are defined in the domain \{2,8,10\}

  1. (f-g)2 = f(2) - g(2) = -1

(f-g)(8) = -5

(f-g)(10) = -16

Thus,(f-g) = \left \{(2,-1),(8,-5),(10,16)\right \}

  1. (f+g) (2)= f(2) + g(2) = 9

(f+g)(8) = 3

(f+g)(10) = 10

Thus, (f+g) = \left \{(2,9),(8,3),(10,10)\right \}

  1. (f.g)(2) = f(2) . g(2) = 20

(f.g) (8)= -4

(f.g)(10) = -39

Thus, (f.g) = \left \{(2,20),(8,-4),(10,-39)\right \}

  1. (f/g)(2) = f(2)/g(2) = 4/52(f/g) = f(2)/g(2) = 4/5

(f/g)(8) = -1/4

(f/g)(10) = -3/13

Thus, V = \left \{(2,4/5), (8,(-1/4), (10,-3/13)\right \}

Thus, the correct matches will be-

(a)\rightarrow (iii), (b)\rightarrow (iv), (c) \rightarrow (ii) \& (d) \rightarrow (i)

Question:38

The ordered pair (5,2) belongs to the relation R =\left \{(x,y): y = x - 5, x,y \in Z \right \}

Answer:

Given data:R =\left \{(x,y): y = x - 5, x,y \in Z \right \}

Now, for (5,2),

Y = x-5

Putting x = 5 \: \: and\: \: y = 5-5 = 0\neq2

Thus, (5,2) is not the ordered pair of R, hence it is false.

Question:39

If P = \left \{1, 2\right \}, then P \times P \times P = \left \{(1, 1,1), (2,2, 2), (1, 2,2), (2,1, 1)\right \}

Answer:

Given data: P = \left \{1, 2\right \}

Now, P \times P = \left \{1,2\right \} \times \left \{1,2\right \}

= \left \{(1,1),(1,2),(2,1),(2,2)\right \}

& P \times P \times P = \left \{1,2\right \} \times \left \{1,2\right \} \times \left \{1,2\right \}

= \left \{(1,1,1),(1,1,2),(1,2,1),(1,2,2),(2,1,1),(2,1,2),(2,2,1),(2,2,2)\right \}

Thus, the statement is false.

Question:40

If A= \left \{1,2, 3\right \}, 5= \left \{3,4\right \} and\: \: C= \left \{4, 5, 6\right \}, then(A \times B) \cup (A \times C) = \left \{(1, 3), (1, 4), (1, 5), (1, 6), (2, 3), (2, 4), (2, 5), (2, 6), (3, 3), (3,4), (3, 5), (3,6)\right \}.

Answer:

Given data: A= \left \{1,2, 3\right \}, 5= \left \{3,4\right \} and\: \: C= \left \{4, 5, 6\right \}

Now,A \times B = \left \{(1,3),(1,4),(2,3),(3,3),(3,4)\right \}

A \times C = \left \{(1,4),(1,5),(1,6),(2,4),(2,5),(2,6),(3,4),(3,5),(3,6)\right \}

Now,(A \times B) \cup (A \times C) = \left \{(1,3),(1,4),(1,5),(1,6),(2,3),(2,4),(2,5),(2,6),(3,3),(3,4),(3,5),(3,6)\right \}.

Thus, the given statement is true.

Question:41

State True or False for the following statements

If(x - 2, y + 5) = \left ( -2,\frac{1}{3} \right ) are two equal ordered pairs, thenx = 4, y=\frac{-14}{3}.

Answer:

Given data: (x - 2, y + 5) = \left ( -2,\frac{1}{3} \right )

Now,x - 2 = -1, i.e., x = 0 & y +5 = 1/3, thus, y = -14/3

Thus, the given statement is false.

Question:42

If A\times B= \left \{(a, x), (a, y), (b, x), (b, y)\right \}, then M = \left \{a, b\right \},B= \left \{x, y\right \}.

Answer:

Given data: A = \left \{a,b\right \} , B = \left \{x,y\right \}

A \times B = \left \{(a,x),(a,y),(b,x),(b,y)\right \}

Therefore, the statement is true.

More About NCERT Exemplar Class 11 Maths Chapter 2

NCERT Exemplar Class 11 Maths chapter 2 solutions are very useful and will help the students in understanding different concepts thoroughly. NCERT Exemplar Class 11 Maths solutions chapter 2 pdf download offers a step-wise explanation of the questions making it easy for the students to understand the concept and the method easily.

Main Subtopics in NCERT Exemplar Class 11 Maths Solutions Chapter 2 Relations and Functions

  • 2.1 Overview
  • 2.1.1 Cartesian Product of sets
  • 2.1.2 Relations
  • 2.1.3 Functions
  • 2.1.4 Some specific types of functions
  • i. Identity function
  • ii. Constant function
  • iii. Polynomial function
  • iv. Rational function
  • v. Modulus function
  • vi. Signum function
  • vii. Greatest integer function
  • 2.1.5 Algebra of real sets
  • i. Addition of two real functions
  • ii. Subtraction of a real function from another
  • iii. Multiplication by a scalar
  • iv. Multiplication of two real functions
  • v. Quotient of two real functions

2.2 Solved examples

What will the students learn through NCERT Exemplar Class 11 Maths Solutions Chapter 2?

Through Class 11 Maths NCERT Exemplar solutions chapter 2, the students will learn briefly about different types of relations and functions along with different functions associated with them. NCERT Exemplar solutions for Class 11 Maths Chapter 2 will help students in further learning about sets and will help them to relate this concept to real life situations. With NCERT Exemplar Class 11 Maths solutions chapter 2, the students will understand the use of function and relation in daily routine. It can also be related to different marks a student scores during different semesters for college or different scores of exams in a year at the school of a particular student is seen as established through the use of relation and functions.

NCERT Solutions for Class 11 Mathematics Chapters

Important topics to cover in NCERT Exemplar Class 11 Maths Solutions Chapter 2 Relations and Functions

  • NCERT Exemplar solutions for Class 11 Maths chapter 2 defines a function which is denoted by f and defines relation f from set S to T as a function only if set S has only one image in set T.

  • NCERT Exemplar Class 11 Maths chapter 2 solutions also defines various terms related to function including domain, co-domain and range and their identification indifferent sets of relations and functions along with the interpretation of different kinds of functions as identity function, constant function, polynomial function, modulus function, rational function, signum function, and greatest integer function.

  • NCERT Exemplar Class 11 Maths solutions chapter 2 also covers different algebra for a real function includes addition, subtraction multiplication, and quotient with the help of given illustrations and examples. It also contains a variety of numerical for practice and illustration of different kinds of questions relating to relations and functions and operations associated with it.


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Frequently Asked Questions (FAQs)

1. How is this chapter helpful for higher education?

This chapter is one of the basic chapters of calculus maths and is helpful in solving many problems related to maths and physics during higher education and engineering.

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Yes, these NCERT Exemplar Class 11 Maths solutions chapter 2 are available offline as one can download these solutions through a download link.

3. How many questions are solved in these solutions?

Our team has solved 23 questions from three exercises along with 12 miscellaneous questions mentioned in the NCERT book.

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A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

Option 1)

0.34\; J

Option 2)

0.16\; J

Option 3)

1.00\; J

Option 4)

0.67\; J

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times.  Assume that the potential energy lost each time he lowers the mass is dissipated.  How much fat will he use up considering the work done only when the weight is lifted up ?  Fat supplies 3.8×107 J of energy per kg which is converted to mechanical energy with a 20% efficiency rate.  Take g = 9.8 ms−2 :

Option 1)

2.45×10−3 kg

Option 2)

 6.45×10−3 kg

Option 3)

 9.89×10−3 kg

Option 4)

12.89×10−3 kg

 

An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

Option 1)

2,000 \; J - 5,000\; J

Option 2)

200 \, \, J - 500 \, \, J

Option 3)

2\times 10^{5}J-3\times 10^{5}J

Option 4)

20,000 \, \, J - 50,000 \, \, J

A particle is projected at 600   to the horizontal with a kinetic energy K. The kinetic energy at the highest point

Option 1)

K/2\,

Option 2)

\; K\;

Option 3)

zero\;

Option 4)

K/4

In the reaction,

2Al_{(s)}+6HCL_{(aq)}\rightarrow 2Al^{3+}\, _{(aq)}+6Cl^{-}\, _{(aq)}+3H_{2(g)}

Option 1)

11.2\, L\, H_{2(g)}  at STP  is produced for every mole HCL_{(aq)}  consumed

Option 2)

6L\, HCl_{(aq)}  is consumed for ever 3L\, H_{2(g)}      produced

Option 3)

33.6 L\, H_{2(g)} is produced regardless of temperature and pressure for every mole Al that reacts

Option 4)

67.2\, L\, H_{2(g)} at STP is produced for every mole Al that reacts .

How many moles of magnesium phosphate, Mg_{3}(PO_{4})_{2} will contain 0.25 mole of oxygen atoms?

Option 1)

0.02

Option 2)

3.125 × 10-2

Option 3)

1.25 × 10-2

Option 4)

2.5 × 10-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

Option 1)

decrease twice

Option 2)

increase two fold

Option 3)

remain unchanged

Option 4)

be a function of the molecular mass of the substance.

With increase of temperature, which of these changes?

Option 1)

Molality

Option 2)

Weight fraction of solute

Option 3)

Fraction of solute present in water

Option 4)

Mole fraction.

Number of atoms in 558.5 gram Fe (at. wt.of Fe = 55.85 g mol-1) is

Option 1)

twice that in 60 g carbon

Option 2)

6.023 × 1022

Option 3)

half that in 8 g He

Option 4)

558.5 × 6.023 × 1023

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m2 , the number of rotations made by the pulley before its direction of motion if reversed, is

Option 1)

less than 3

Option 2)

more than 3 but less than 6

Option 3)

more than 6 but less than 9

Option 4)

more than 9

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