How many quadruples of positive integers lying in between and ( and inclusive) are there which satisfy ?
Solution
Let , , . Then, are integers satisfying . Furthermore, since , we see that the triple must be one of the following triples:
When , we get . So, corresponding to the cases , we get quadruples satisfying the required condition. Similarly, when , we get quadruples satisfying the requirement corresponding to the cases . We also find if or if only quadruple corresponding to will satisfy the requirement. Therefore, there are only quadruples satisfying the requirement.
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