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Ratio Sum Equation (Posted on 2016-10-09) Difficulty: 3 of 5
Find all possible nonzero integer solutions to this equation:
 13      1996      Z
---- +  ------- = ----
 M2       N2       1997
Prove that no further solution to the above equation is possible.

No Solution Yet Submitted by K Sengupta    
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Some Thoughts Some analytic progress Comment 2 of 2 |
As Jer noted, it will suffice to focus on positive integer solutions.

I started be clearing fractions. This got me
13*1997*N^2 + 1996*1997*M^2 = M^2*N^2*Z
Multiply by Z and move to one side
(M^2*Z)*(N^2*Z) - 13*1997*N^2*Z - 1996*1997*M^2*Z = 0
Then add (13+1996)*1997 to each side and factor:
(M^2*Z - 13*1997) * (N^2*Z - 1996*1997) = 7^2*41*1997

Then at this point the right side has 12 distinct ordered factorizations, corresponding to possible (M^2*Z, N^2*Z).  At this point it gets tedious to list out solution sets.  Maybe I will come back and grind out the numbers later.

Edited on January 3, 2025, 7:07 pm
  Posted by Brian Smith on 2025-01-03 19:06:32

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