Prove that there are no positive integers and such that
Solution
Let us write the equation in the form
and note that and are relatively prime numbers. We consider two cases:
a) and for some positive integers and .
Inequality is equivalent to the inequality , which holds for all positive integers . Also, we have .
Hence, , which is impossible.
b) and for some positive integers and .
From the second equation we conclude that cannot be divisible by . If we have , then . If we have , then , and if , then . In all cases the left-hand side of the equation cannot be divisible by .
Hence the equation has no solution.
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