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Power Crossed Cube Conclusion (Posted on 2023-04-01) Difficulty: 3 of 5
Determine all triplet(s) (p, q, r) of positive integers that satisfy the equation:
          (5)p * (43)q + 1 = r3

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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Computer solution | Comment 2 of 3 |
I also found only one solution:  (p,q,r) = (1,1,6) which I suspect is the only solution, but it would be nice to have an analytical proof of that.

Due to the 5^p term, the LHS is always 6 mod 10, so r^3 must be also.  
Therefore the last digit of r can only be 6.

------

big = 200
for p in range(1,big):
    for q in range(1,big):
        for r in range(6,big,10):
            if (5)**p * (43)**q + 1 == r**3:
                print(p,q,r)
Output: 1 1 6

  Posted by Larry on 2023-04-01 11:40:26
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