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Q.Let A={x∈W:x<3}A=\{x \in W : x<3\}, B={x∈N:2≤x≤5}B=\{x \in N : 2 \le x \le 5\} and C={3,5}C=\{3,5\}, verify that A×(B∪C)=(A×B)∪(A∪B)A \times (B \cup C) = (A \times B) \cup (A \cup B)

Manipur CohsemCouncil of Higher Secondary Education, Manipur (Higher Secondary 1st Year) 2026Subjective· 4mImportance★★★★★
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Both sides of the identity work out to the same set of 12 ordered pairs, verifying A×(B∪C) = (A×B)∪(A×C).

(Note: the standard identity being verified here is A×(B∪C) = (A×B)∪(A×C); the printed "∪B" in the stem appears to be a typo for "×C" — this is the well-known distributive law of Cartesian product over union, which is what this question is testing.)

First list the sets: W = whole numbers {0,1,2,3,...}, so A={x∈W:x<3}={0,1,2}A=\{x\in W: x<3\} = \{0,1,2\}.

N = natural numbers {1,2,3,...}, so B={x∈N:2≤x≤5}={2,3,4,5}B=\{x\in N: 2\le x\le5\} = \{2,3,4,5\}.

C={3,5}C=\{3,5\}.

LHS: B∪C={2,3,4,5}∪{3,5}={2,3,4,5}B\cup C = \{2,3,4,5\}\cup\{3,5\} = \{2,3,4,5\} (C is already a subset of B).

A×(B∪C)={0,1,2}×{2,3,4,5}A\times(B\cup C) = \{0,1,2\}\times\{2,3,4,5\} = the 12 pairs (0,2),(0,3),(0,4),(0,5),(1,2),(1,3),(1,4),(1,5),(2,2),(2,3),(2,4),(2,5).

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