Which option correctly writes J={3,6,9,12} in set-builder form?
Answer and explanation
Correct answer: J={x: x=3n, n∈N, 1≤n≤4}
Set-builder form describes members through a rule and restrictions. In option A, let n be 1, 2, 3, and 4; then x=3n gives 3, 6, 9, and 12, exactly the elements of J. Option B gives 2, 4, 6, 8; option C stops at n=3 and omits 12; option D gives 4, 8, and 12. Hence only option A represents the given set completely.
Frequently asked questions
What is the correct answer to this question?
J={x: x=3n, n∈N, 1≤n≤4}
Why is this the correct answer?
Set-builder form describes members through a rule and restrictions. In option A, let n be 1, 2, 3, and 4; then x=3n gives 3, 6, 9, and 12, exactly the elements of J. Option B gives 2, 4, 6, 8; option C stops at n=3 and omits 12; option D gives 4, 8, and 12. Hence only option A represents the given set completely.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Common Questions.
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