SOLUTION: Find a counterexample to the following statement: If p is a prime number, then 2p-1 is prime.

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Find a counterexample to the following statement: If p is a prime number, then 2p-1 is prime.       Log On


   

Question 13443: Find a counterexample to the following statement:
If p is a prime number, then 2p-1 is prime.
Answer by rapaljer(4671) About Me  (Show Source):
You can put this solution on YOUR website!
How about 5, 13, or 23? There are a TON of examples of primes p such 2p-1 is NOT a prime.

5*2-1 = 9 which is NOT a prime.
2*13 - 1 = 25 which is NOT a prime.
2*23 - 1 = 45 which is NOT a prime.

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