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Question Observe that 3 is a prime number, and 2 × 3 + 1 = 7 is also a prime.
Are there other primes for which doubling and adding 1 gives another prime? Find at least five such examples.
We can have primes as:
2 × 2 + 1 = 5, prime number;
2 × 5 + 1 = 11, prime number;
2 × 11 + 1= 23, prime number;
2 × 23 + 1 = 47, prime number;
2 × 29 + 1 = 59, primfe number;
and 2 × 41 + 1 = 83, prime number;
Thus, 2, 5, 11, 23, 29 and 41 are required primes. (Answer may vary)
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