Solve all your doubts with Teachoo Black (new monthly pack available now!)
Misc 11 - Chapter 1 Class 11 Sets (Term 1)
Last updated at Sept. 3, 2021 by Teachoo
Miscellaneous
Misc 1
Misc 2 (i)
Misc 2 (ii) Important
Misc 2 (iii) Important
Misc 2 (iv)
Misc 2 (v)
Misc 2 (vi) Important
Misc 3
Misc 4 Important
Misc 5
Misc 6 Deleted for CBSE Board 2023 Exams
Misc 7 Important Deleted for CBSE Board 2023 Exams
Misc 8 Important
Misc 9 Important
Misc 10
Misc 11 You are here
Misc 12 Important
Misc 13 Important
Misc 14
Misc 15 Important
Misc 16 Important
Transcript
Misc 11 Let A and B be sets. If A ∩ X = B ∩ X = ∅ and A ∪ X = B ∪ X for some set X, show that A = B. (Hints: A = A ∩ (A ∪ X), B = B ∩ (B ∪ X) and use distributive law) Given: Let A and B be two sets such that A ∩ X = B ∩ X = ∅ and A ∪ X = B ∪ X for some set X. To prove: A = B Proof: Let A = A ∩ (A ∪ X) A = A ∩ (B ∪ X) Let A = A ∩ (A ∪ X) Given A ∪ X = B ∪ X A = A ∩ (B ∪ X) Using distributive law : A ∩ (B ∪ C)= (A ∩ B) ∪ (A ∩ C) = (A ∩ B) ∪ (A ∩ X) As A ∩ X = ∅ given = (A ∩ B) ∪ ∅ A = A ∩ B Let B = B ∩ (B ∪ X) Given A ∪ X = B ∪ X B = B ∩ (A ∪ X) Using distributive law: A ∪ (B ∩ C)= (A ∩ B) ∪ (A ∩ C) = (B ∩ A) ∪ (B ∩ X) As B ∩ X = Φ = (B ∩ A) ∪ Φ B = B ∩ A B = A ∩ B From (1) and (2), A = A ∩ B & B = A ∩ B ∴ A = B Hence proved
