Which of the following is equal to A ∪ A?
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Answer and explanation
Correct answer: A
Taking the union of a set with itself does not introduce any new elements. Every element of A is already in the first copy and the second copy, so A ∪ A = A. This is called the idempotent law. In contrast, A − A = ∅ and A ∩ ∅ = ∅, so those expressions are not generally equal to A.
Frequently asked questions
What is the correct answer to this question?
A
Why is this the correct answer?
Taking the union of a set with itself does not introduce any new elements. Every element of A is already in the first copy and the second copy, so A ∪ A = A. This is called the idempotent law. In contrast, A − A = ∅ and A ∩ ∅ = ∅, so those expressions are not generally equal to A.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Equal sets and Subsets.
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