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Powered Radicals (Posted on 2025-03-17) Difficulty: 3 of 5
If
(√6 + √2)9   A + B√C
---------- = -------
  (√8)9         D
Then, find the integers values of A, B, C, and D with C square-free.

No Solution Yet Submitted by K Sengupta    
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Solution Analytic solution | Comment 5 of 7 |
Sometimes I choose a computer solution because it looks like it might be more fun, or faster.  But this time, I didn't.

(√6 + √2)^9 = √2^9 * (1 + √3)^9
= 16√2 * (1 + √3)^9

(1 + √3)^9 = 
1 + 9√3 + 36*3 + 84*3√3 + 126*9 + 126*9√3 +  84*27 + 36*27√3 + 9*81 + 81√3
= 4240 + 2448√3
    

(√8)^9 = √8*8^4 = 8192√2

LHS:  16√2 * (4240 + 2448√3)
      ----------------------
               8192√2

LHS:  16^2 * (265 + 153√3)
      ----------------------
               8192 

LHS:  (265 + 153√3)
      -------------
           32 

 A + B√C       265 + 153√3
--------- =    ---------  
   D               32

(A,B,C,D) = (256,153,3,32)


  Posted by Larry on 2025-03-17 12:44:15
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