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Reciprocals pairs (Posted on 2025-02-13) Difficulty: 3 of 5
Find all integer pairs (x, y) that satisfy the equation
  x       y
----- + ----- = 1
y + 7   x + 7

No Solution Yet Submitted by Danish Ahmed Khan    
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Some Thoughts brute force | Comment 3 of 5 |
Clearly by inspection x=y=7 is one solution.

There are seven other solutions where x and y are different (fourteen if you swap x and y).

Fifteen solutions total.
(-8,-5),(-8,-3),(-5,-8),(-5,3),(-3,-8),(-3,5),(0,7),(3,-5),(3,8),(5,-3),(5,8),(7,0),(7,7),(8,3),(8,5)

If the equation is rearranged to avoid dividing by zero, there are three other solutions involving x and/or y being -7:
(-7,-7),(-7,0),(0,-7)  but these do not solve the equation as presented.

  Posted by Larry on 2025-02-13 17:33:52
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