Check sibling questions

Example 30 - Show that A U B = AB implies A = B - Chapter 1 Sets

Example 30 - Chapter 1 Class 11 Sets - Part 2
Example 30 - Chapter 1 Class 11 Sets - Part 3

This video is only available for Teachoo black users

Introducing your new favourite teacher - Teachoo Black, at only ₹83 per month


Transcript

Example 30 Show that A ∪ B = A ∩ B implies A = B In order to prove A = B, we should prove A is a subset of B i.e. A ⊂ B & B is a subset of A i.e. B ⊂ A Let x ∈ A. Then, x ∈ A ∪ B. Since A ∪ B = A ∩ B , ∴ x ∈ A ∩ B. So, x ∈ B. ∴ If x ∈ A , then x ∈ B i.e. if an elements belongs to set A, then it must belong to set B also Therefore, A ⊂ B. Similarly, if y ∈ B, then y ∈ A ∪ B. Since A ∪ B = A ∩ B, y ∈ A ∩ B. So, y ∈ A. ∴ If y ∈ B , then y ∈ A …(1) i.e. if an elements belongs to set B, then it must belong to set A also Therefore, B ⊂ A. From (1) & (2) A ⊂ B & B ⊂ A Thus, A = B Hence shown

Davneet Singh's photo - Teacher, Engineer, Marketer

Made by

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.