# Example 17 - Chapter 1 Class 12 Relation and Functions

Last updated at May 29, 2018 by Teachoo

Last updated at May 29, 2018 by Teachoo

Transcript

Example 17 Show that if f : R 7 5 R 3 5 is defined by f(x) = 3 + 4 5 7 and g: R 3 5 R 7 5 is defined by g(x) = 7 + 4 5 3 , then fog = IA and gof = IB, where A = R 3 5 , B = R 7 5 ; IA (x) = x, x A, IB (x) = x, x B are called identity functions on sets A and B, respectively. f(x) = 3 + 4 5 7 & g(x) = 7 + 4 5 3 Finding gof g(x) = 7 + 4 5 3 g(f(x)) = 7 ( ) + 4 5 ( ) 3 gof = 7 3 + 4 5 7 + 4 5 3 + 4 5 7 3 = 7 3 + 4 + 4(5 7) 5 7 5 3 + 4 3(5 7) 5 7 = 7 3 + 4 + 4(5 7) 5 3 + 4 3(5 7) = 21 + 28 + 20 28 15 + 20 15 + 21 = 41 41 = x Thus, gof = x = IB Finding fog f(x) = 3 + 4 5 7 f(g(x)) = 3 ( ) + 4 5 ( ) 7 = 3 7 + 4 5 3 + 4 5 7 + 4 5 3 3 = 3 7 + 4 + 4(5 3) 5 3 5 7 + 4 3(5 3) 5 3 = 3 7 + 4 + 4(5 3) 5 7 + 4 3(5 3) = 21 + 12 + 20 12 35 + 20 35 + 21 = 41 41 = x Thus, fog = x = IA

Examples

Example 1

Example 2

Example 3

Example 4

Example 5

Example 6

Example 7

Example 8

Example 9

Example 10

Example 11

Example 12

Example 13

Example 14

Example 15

Example 16

Example 17 You are here

Example 18

Example 19

Example 20

Example 21

Example 22

Example 23 Important

Example 24

Example 25 Important

Example 26

Example 27

Example 28

Example 29

Example 30

Example 31

Example 32

Example 33

Example 34

Example 35

Example 36

Example 37

Example 38

Example 39

Example 40

Example 41

Example 42

Example 43

Example 44

Example 45

Example 46 Important

Example 47 Important

Example 48 Important

Example 49

Example 50

Example 51

Chapter 1 Class 12 Relation and Functions

Serial order wise

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.