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1. |
Show that the following four conditions are equivalent(i) A ⊂ B(ii) A – B=φ(iii) A ∪ B = B(iv) A ∩ B A. |
Answer» (i) ⇔ (ii): A⊂B ⇔ All elements of A are in B ⇔ A – B = φ (ii) ⇔ (iii): A-B = φ⇔ All elements of A are in B ⇔ A∪B = B (iii) ⇔(iv) A∪B = B ⇔ All elements of A are in B ⇔ All elements of A are common in A and B. ⇔ A∩B = A ∴ All the four given conditions are equivalent. |
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