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      Question

      If (x - 1) 3  + (y - 2) 3  + (z

      - 3) 3  + 3(x + y - 3)(y + z - 5)(x + z - 4) = 0, then what is the value of (x + y + z)?
      A 8 Correct Answer Incorrect Answer
      B 2 Correct Answer Incorrect Answer
      C 3 Correct Answer Incorrect Answer
      D 6 Correct Answer Incorrect Answer

      Solution

      As we know, (a + b + c) 3  = a 3  + b 3  + c 3  + 3(a + b)(b + c)(a + c)

      Then, here, a = x - 1, b = y - 2 and c = z - 3

      Now, according to the question:

      a 3  + b 3  + c 3  + 3(a + b)(b + c)(a + c) = 0

      So, (a + b + c) 3  = 0

      (a + b + c) = 0

      Then, (x - 1 + y - 2 + z - 3) = 0

      Therefore, (x + y + z) = 6

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