If A − B = A ∩ B', then (A − B)' is equal to which expression?
Answer and explanation
Correct answer: A' ∪ B
Use the given identity A − B = A ∩ B'. Taking complements on both sides gives (A − B)' = (A ∩ B')'. Applying De Morgan's law, (X ∩ Y)' = X' ∪ Y', we obtain (A ∩ B')' = A' ∪ (B')' = A' ∪ B. Therefore, option A is correct. The key step is to rewrite set difference before taking the complement.
Frequently asked questions
What is the correct answer to this question?
A' ∪ B
Why is this the correct answer?
Use the given identity A − B = A ∩ B'. Taking complements on both sides gives (A − B)' = (A ∩ B')'. Applying De Morgan's law, (X ∩ Y)' = X' ∪ Y', we obtain (A ∩ B')' = A' ∪ (B')' = A' ∪ B. Therefore, option A is correct. The key step is to rewrite set difference before taking the complement.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Complement of a Set and Its Properties.