Find all ordered triples of positive reals that satisfy: , and , where denotes the greatest integer less than or equal to .
Solution
Write . Note that is an integer. Multiplying the three equations gives: Substitution into the first equation, Looking at the last equation: Here we've used , and also the apparent fact that . Now: Since is an integer, we must have . Since is a product of 3 positive integers, we must have those be 1,1 , and 2 in some order, so there are three cases: Case 1: . By the equations, we'd need , a contradiction, so there are no solutions in this case. Case 2: . We have the solution Case 3: . We have the solution
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