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Brazil number theory

Problem

Show that there are only finitely many solutions to in positive integers.
Solution
Suppose without loss of generality that . We must have , otherwise . So there are only finitely many possible values for .

Now consider the number of solutions for fixed . We have . Now we must have , otherwise . So there are only finitely many possible values for . The number is fixed once and are fixed, so we have shown that there are only finitely many solutions.

Techniques

Techniques: modulo, size analysis, order analysis, inequalitiesIntegers