Problem:
Determine all integers such that the product is the square of an integer.
Solution
Solution:
The answers are , , and , for all of which the product is .
Assume that there is another solution. We can immediately rule out the case , as then the product is negative. So is a positive integer. Note that the greatest common divisor of and is , as two consecutive integers cannot be multiples of the same prime. Likewise, and so . Now and are relatively prime positive integers whose product is a square, so they must both be squares (any prime dividing either of them must do so to an even power). But , so now and are two consecutive positive integers which are both squares, which is impossible (the difference between any two consecutive squares and is ).
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