Determine all pairs of integers such that
Solution
The factorization of the right hand side of the equation gives us
Since , obtained factors are consecutive integers.
First we assume that all the factors, , and are different from zero. Since the left hand side of the equality is positive, these three factors also have to be positive.
It follows that and are relatively prime (since and are relatively prime and also and are relatively prime). The product of two relatively prime positive integers is a perfect square if and only if each of the numbers is a perfect square. In particular, that means that
is a perfect square. Therefore, and are two consecutive integers which are both perfect squares, and that is possible if and only if those numbers are zero and one. Hence,
so or . But then or , which is a contradiction with the assumption that all the factors are different from zero.
If one of the factors on the right hand side is equal to zero, then and we get the solutions