What is the roster form of L={x: x∈N and x²<20}?
Answer and explanation
Correct answer: L={1,2,3,4}
Use the condition x²<20 for natural numbers. The successive values are 1²=1, 2²=4, 3²=9, and 4²=16, all less than 20. The next value is 5²=25, which fails the inequality. Under the usual school convention N={1,2,3,...}, zero is not included. Hence the complete roster is {1,2,3,4}, making option A correct; B includes zero and C includes 5.
Frequently asked questions
What is the correct answer to this question?
L={1,2,3,4}
Why is this the correct answer?
Use the condition x²<20 for natural numbers. The successive values are 1²=1, 2²=4, 3²=9, and 4²=16, all less than 20. The next value is 5²=25, which fails the inequality. Under the usual school convention N={1,2,3,...}, zero is not included. Hence the complete roster is {1,2,3,4}, making option A correct; B includes zero and C includes 5.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Common Questions.
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