Find all natural numbers and prime numbers such that is a natural number.
, 2012
Solution
Denote where is a natural number, hence . Thus is a divisor of . Since is prime, we have or (but is not prime). So .
Now, .
Try : .
Try : (not integer).
Try : (not integer).
So only , , is a solution.
Alternatively, if the original problem was (as in the solution context), then must be a divisor of , so or .
For : .
For : (not integer).
Thus, the only solution is , , .
Therefore, the solutions are , .
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