यदि \(A={x:x\in\mathbb{N},3\mid x,x\le 21}\) और \(B={x:x\in\mathbb{N},7\mid x,x\le 21}\) हैं, तो \(A\cup B\) क्या है?
If \(A={x:x\in\mathbb{N},3\mid x,x\le 21}\) and \(B={x:x\in\mathbb{N},7\mid x,x\le 21}\), what is \(A\cup B\)?
Explanation opens after your attempt
A. ( {3,6,7,9,12,14,15,18,21} )
Concept
(A) has multiples of (3), and (B) has multiples of (7). In the union, do not write (21) twice.
Why this answer is correct
The correct answer is A. ( {3,6,7,9,12,14,15,18,21} ). (A) has multiples of (3), and (B) has multiples of (7). In the union, do not write (21) twice.
Exam Tip
(A) में (3) के गुणज और (B) में (7) के गुणज हैं। संघ में (21) को दो बार नहीं लिखते।
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