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Non Prime Integer Inquiry (Posted on 2024-02-29) Difficulty: 3 of 5
The positive integers x and y satisfy the equation

x2 – y2 = 2026 – 2(x + 2y)

Given that neither x nor y is prime, find the value of xy.

No Solution Yet Submitted by Danish Ahmed Khan    
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Solution computer solution | Comment 2 of 3 |
for tot=2:100000
  for x=1:tot-1
    y=tot-x;
    if x^2-y^2==2026-2*(x+2*y)
      disp([x,y])
      factor(x)
      factor(y)
      disp(' ')
    end
  end
end

finds

>> nonPrimeIntegerInquiry
    67    53
ans =
    67
ans =
    53
 
   147   143
ans =
     3     7     7
ans =
    11    13
 
        1011        1013
ans =
     3   337
ans =
        1013
        
(67, 53) satisfy the equation but both are prime.

(1011, 1013) satisfy the equation, but the latter, y = 1013, is prime.

x = 147, y = 143 satisfy the equation and neither is prime, as

147 = 3*7^2   and   143 = 11*13

The answer is thus 147*143 = 21021.

  Posted by Charlie on 2024-02-29 08:13:23
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