Find all the prime numbers for which there exist positive integers and that satisfy the equation
Solution
Given equation is equivalent to
We consider the following cases:
1. Let and . For prime the equation has no solutions.
2. Let and . For prime the equation has the determinant . The inequality implies . For we obtain the solutions and .
For we obtain the solutions and .
3. Let and . For prime the equation has the diskriminant . The inequality implies .
Let with . We obtain the equation which is equivalent to
It follows that both numbers and shall be even. We have two subcases:
a) and . We have , which is no prime.
b) and . We obtain and . The equation has the solutions and .
4. Let and . It follows that .
So, the equation has natural solutions only for .
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