# 10TH MATHS CHAPTER 1 RELATIONS AND FUNCTIONS EXERCISE 1.4 Guide

10th Standard Maths Chapter 1 Exercise 1.4 Relations and Functions Guide Book Back Answers Solutions. TN 10th SSLC Samacheer Kalvi Guide. 10th All Subject Guide – Click Here. Class 1 to 12 All Subject Book Back Answers – Click Here.

## 10th MATHS CHAPTER 1 – RELATIONS AND FUNCTIONS – EXERCISE 1.4 Guide

### 1. Determine whether the graph given below represents functions. Give a reason for your answers concerning each graph.

**Solu.:**

(i) It is not a function. The graph meets the vertical line at more than one point.

(ii) It is a function as the curve meets the vertical line at only one point.

(iii) It is not a function as it meets the vertical line at more than one point.

(iv) It is a function as it meets the vertical line at only one point.

### 2. Let f :A → B be a function defined by f(x) = x2 – 1, Where A = {2, 4, 6, 10, 12},

B = {0, 1, 2, 4, 5, 9}. Represent f by

- (i) set of ordered pairs;
- (ii) a table;
- (iii) an arrow diagram;
- (iv) a graph

**Solu.:**

f: A → B

A = {2, 4, 6, 10, 12}, B = {0, 1, 2, 4, 5, 9}

(i) Set of ordered pairs

= {(2, 0), (4, 1), (6, 2), (10, 4), (12, 5)}

(ii) a table

(iii) an arrow diagram;

### 3. Represent the function f = {(1, 2),(2, 2),(3, 2), (4,3), (5,4)} through

- (i) an arrow diagram
- (ii) a table form
- (iii) a graph

**Solu.:**

f = {(1, 2), (2, 2), (3, 2), (4, 3), (5, 4)}

(i) An arrow diagram.

### 4. Show that the function f: N → N defined by f{x) = 2x – 1 is one – one but not onto.

**Solu.:
**f: N → N

f(x) = 2x – 1

N = {1, 2, 3, 4, 5,…}

f(1) = 2(1) – 1 = 1

f(2) = 2(2) – 1 = 3

f(3) = 2(3) – 1 = 5

f(4) = 2(4) – 1 = 7

f(5) = 2(5) – 1 = 9

In the figure, for different elements in x, there are different images in f(x).

Hence f : N → N is a one-one function.

A function f: N → N is said to be onto function if the range of f is equal to the co-domain of f

Range = {1, 3, 5, 7, 9,…}

Co-domain = {1, 2, 3,..}

But here the range is not equal to co-domain. Therefore it is one-one but not onto function.

### 5.Show that the function f: N → N defined by f (m) = m2 + m + 3 is one – one function.

**Solution:**

f: N → N

f(m) = m2 + m + 3

N = {1, 2, 3, 4, 5…..}m ∈ N

f{m) = m2 + m + 3

f(1) = 12 + 1 + 3 = 5

f(2) = 22 + 2 + 3 = 9

f(3) = 32 + 3 + 3 = 15

f(4) = 42 + 4 + 3 = 23

In the figure, for different elements in the (X) domain, there are different images in f(x). Hence f: N → N is one-to-one but not onto function as the range of f is not equal to the co-domain.

Hence it is proved.

### 6. Let A = {1,2, 3, 4} and B = N .

Let f: A → B be defined by f(x) = x3 then,

- (i) find the range of f
- (ii) identify the type of function

**Solu.:
**A = {1,2, 3,4}

B = {1,2, 3, 4, 5,….}

f(x) = x3

f(1) = 13 = 1

f(2) = 23 = 8

f(3) = 33 = 27

f(4) = 43 = 64

(i) Range = {1,8, 27, 64}

(ii) one -one and into function.

### 7. In each of the following cases state whether the function is bijective or not. Justify your answer.

- (i) f: R → R defined by f(x) = 2x + 1
- (ii) f: R → R defined by f(x) = 3 – 4×2

**Solu.:**

(i) f : R → R

f(x) = 2x + 1

f(1) = 2(1) + 1 = 3

f(2) = 2(2) + 1 = 5

f(-1) = 2(-1) + 1 = -1

f(0) = 2(0) + 1 = 1

It is a bijective function. Distinct elements of A have distinct images in B and every element in B has a pre-image in A.

(ii) f: R → R; f(x) = 3 – 4×2

f(1) = 3 – 4(12) = 3 – 4 = -1

f(2) = 3 – 4(22) = 3 – 16 = -13

f(-1) = 3 – 4(-1)2 = 3 – 4 = -1

It is not a bijective function since it is not one-one

### 8. Let A = {-1, 1} and B = {0, 2}. If the function f: A → B defined by f(x) = ax + b is an onto function? Find a and b.

**Solu.:
**A= {-1, 1},B = {0, 2}

f: A → B, f(x) = ax + b

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

f(1) = a(1) + b = a + b

Since f(x) is onto, f(-1) = 0

⇒ -a + b = 0 …(1)

& f(1) = 2

⇒ a + b = 2 …(2)

-a + b = 0

### 9. If the function f is defined by

- (i) f(3)
- (ii) f(0)
- (iii) f(-1.5)
- (iv) f(2) + f(-2)

**Solu.:**

(i) f(3) ⇒ f(x) = x + 2 ⇒ 3 + 2 = 5

(ii) f(0) ⇒ 2

(iii) f (- 1.5) = x – 1

= -1.5 – 1 = -2.5

(iv) f(2) + f(-2)

f(2) = 2 + 2 = 4 [∵ f(x) = x + 2]

f(-2) = -2 – 1 = -3 [∵ f(x) = x – 1]

f(2) + f(-2) = 4 – 3 = 1

### 10. A function f: [-5,9] → R is defined as follows:

**Solu.:**

f : [-5, 9] → R

(i) f(-3) + f(2)

f(-3) = 6x + 1 = 6(-3) + 1 = -17

f(2) = 5 × 2 – 1 = 5(22) – 1 = 19

∴ f(-3) + f(2) = -17 + 19 = 2

(ii) f(7) – f(1)

f(7) = 3x – 4 = 3(7) – 4 = 17

f(1) = 6x + 1 = 6(1) + 1 = 7

f(7) – f(1) = 17 – 7 = 10

(iii) 2f(4) + f(8)

f(4) = 5×2 – 1 = 5 × 42 – 1 = 79

f(8) = 3x – 4 = 3 × 8 – 4 = 20

∴ 2f(4) + f(8) = 2 × 79 + 20 = 178

- The distance S an object travels under the influence of gravity in time t seconds is 1 2 given by S(t) = 13gt2+ at + b, where, (g is the acceleration due to gravity), a, b are constants. Check if the function S(t) is one-one.

**Solu.:**

S(t) = 12gt2+ at + b

Let the time be 1, 2, 3 …. n seconds

S(1) = 12g(1)2 + a(1) + b

= g2 + a + b

S(2) = 12 g(2)2 + a(2) + b

= 4g2 + 2a + b

= 2g + 2a + b

S(3) = 12 g(3)2 + a(3) + 6

= 92 g + 3a + b

For every different value of t, there will be different distances.

∴ It is a one-one function.

### 12. The function ‘t’ which maps temperature in Celsius (C) into temperature in Fahrenheit (F) is defined by t(C)= F where F = 9/5 C + 32. Find,

- (i) t(0)
- (ii) t(28)
- (iii) t(-10)
- (iv) the value of C when t(C) = 212
- (v) the temperature when the Celsius value is equal to the Fahrenheit value.

**Solu.:**