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Sorta Platonic... (Posted on 2022-06-09) Difficulty: 4 of 5
Consider this Diophantine equation:
3a + 4b + 5c = 6d, where each of a, b, c, and d is a positive integer.

The famous ancient Greek philosopher and mathematician Plato was aware that a=b=c=d=3 is a solution.

Does there exist any further solution?

Authenticate your answer with valid arguments.

No Solution Yet Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
testing only to the limit of double precision floating point | Comment 2 of 3 |
The comfortable limit for type "double" is d=17, found via logs below. Extra answer is provided by allowing zero exponent, though disallowed in the puzzle statement.

The only set other than (3, 3, 3, 3) that included only positive integers is (3, 1, 1, 2) for 3^3 + 4^1 + 5^1 = 6^2.

Allowing zero in the set yields (0, 1, 0, 1), or 3^0 + 4^1 + 5^0 = 6^1.

3^3 + 4^1 + 5^1 = 6^2

clc, clearvars
for d=0:floor(log(10^14)/log(6))
  remain1=6^d;
  for c=0:floor(log(remain1)/log(5))
    remain2=remain1-5^c;
    for b=0:floor(log(remain2)/log(4))
      remain3=remain2-4^b;
      for a=0:floor(log(remain3)/log(3))
        remain4=remain3-3^a;
        if remain4==0
          disp([a b c d])
        end
      end
    end
  end 
end

having yielded

     a     b     c     d
     
     0     1     0     1
     3     1     1     2
     3     3     3     3

  Posted by Charlie on 2022-06-09 10:08:23
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