Question 7 of 35intermediate🔧 ApplyShort Answer4 marks

Let A={1,2}A = \{1, 2\}, B={1,2,3,4}B = \{1, 2, 3, 4\}, C={5,6}C = \{5, 6\} and D={5,6,7,8}D = \{5, 6, 7, 8\}. Verify that

(i)

A×(B∩C)=(A×B)∩(A×C)A \times (B \cap C) = (A \times B) \cap (A \times C).

Answer

Given A = {1, 2}, B = {1, 2, 3, 4}, C = {5, 6}.

Step 1: Find B ∩ C. B ∩ C = {1, 2, 3, 4} ∩ {5, 6} = φ (empty set, since no common elements)

Step 2: Find A × (B ∩ C). A × (B ∩ C) = A × φ = φ

Step 3: Find A × B. A × B = {(1,1), (1,2), (1,3), (1,4), (2,1), (2,2), (2,3), (2,4)}

Step 4: Find A × C. A × C = {(1,5), (1,6), (2,5), (2,6)}

Step 5: Find (A × B) ∩ (A × C). Since A × B has second elements from {1,2,3,4} and A × C has second elements from {5,6}, there are no common ordered pairs. (A × B) ∩ (A × C) = φ

Conclusion: A × (B ∩ C) = φ = (A × B) ∩ (A × C). Hence verified.

(ii)

A×CA \times C is a subset of B×DB \times D.

Answer

Given A = {1, 2}, B = {1, 2, 3, 4}, C = {5, 6}, D = {5, 6, 7, 8}.

Step 1: Find A × C. A × C = {(1,5), (1,6), (2,5), (2,6)}

Step 2: Find B × D. B × D = {(1,5), (1,6), (1,7), (1,8), (2,5), (2,6), (2,7), (2,8), (3,5), (3,6), (3,7), (3,8), (4,5), (4,6), (4,7), (4,8)}

Step 3: Check if each element of A × C belongs to B × D.

  • (1,5) ∈ B × D (since 1 ∈ B and 5 ∈ D) ✓
  • (1,6) ∈ B × D (since 1 ∈ B and 6 ∈ D) ✓
  • (2,5) ∈ B × D (since 2 ∈ B and 5 ∈ D) ✓
  • (2,6) ∈ B × D (since 2 ∈ B and 6 ∈ D) ✓

Conclusion: Every element of A × C is in B × D. Therefore, A × C ⊆ B × D. Hence verified.

Explanation

This question tests understanding of Cartesian products and set operations. For part (i), the distributive property A × (B ∩ C) = (A × B) ∩ (A × C) is verified by computing both sides. Since B and C have no common elements, B ∩ C = φ, making both sides equal to φ. For part (ii), the subset relation is verified by checking that all first elements of A × C belong to B and all second elements belong to D, which is true since A ⊆ B and C ⊆ D.