Which is the set F = {x : x ∈ N, x is a divisor of 18 and x + 1 is prime}?
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Answer and explanation
Correct answer: F = {1, 2, 6, 18}
The set is formed by filtering the positive divisors of 18 according to a second condition. The divisors are 1, 2, 3, 6, 9, and 18. Adding 1 gives 2, 3, 4, 7, 10, and 19. The prime results are 2, 3, 7, and 19, corresponding to x = 1, 2, 6, and 18. Thus F = {1, 2, 6, 18}; option A is correct.
Frequently asked questions
What is the correct answer to this question?
F = {1, 2, 6, 18}
Why is this the correct answer?
The set is formed by filtering the positive divisors of 18 according to a second condition. The divisors are 1, 2, 3, 6, 9, and 18. Adding 1 gives 2, 3, 4, 7, 10, and 19. The prime results are 2, 3, 7, and 19, corresponding to x = 1, 2, 6, and 18. Thus F = {1, 2, 6, 18}; option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Sets and their representations.
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