Given that and are distinct non-negative real numbers, and let the minimum value of the expression above be denoted as , find .
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Without losing the generally,we may assume:c=min{a,b,c}and → 0 ≤ c < a , b We have: Q ≥ [ ( a + b ) 2 + a 2 + b 2 ] [ ( a − b ) 2 1 + a 2 1 + b 2 1 ] = 2 ( a − b ) 2 a 2 + a b + b 2 + 2 ( b a + a b ) 2 + 2 ( b a + a b ) Let t = b a + a b , t > 2 so Q ≥ f ( t ) = 2 ( t 2 + t + t − 2 t + 1 ) Let considering function f ( t ) = 2 ( t 2 + t + t − 2 t + 1 ) in the range ( 2 ; + ∞ ) we have: f ′ ( t ) = 2 [ 2 t + 1 − ( t − 2 ) 2 3 ] f ′ ( t ) = 0 ⇔ ( 2 t + 1 ) ( t − 2 ) 3 − 3 = 0 ⇔ 2 t 3 − 7 t 2 + 4 t + 1 = 0 ⇔ t = 4 5 + 3 3 ( t > 2 ) Because of t = 4 5 + 3 3 so f'(t) reversal from negative to positive so f ( t ) m i n only when t = 4 5 + 3 3 So f ( t ) ≥ f ( 4 5 + 3 3 ) = 4 5 9 + 1 1 3 f ( t ) m i n = 4 5 9 + 1 1 3 3 .The equality holds when b a + a b = 4 5 + 3 3 , c = 0 .Note that a,b,c maybe permutation. So Q = 4 5 9 + 1 1 3 3 = 3 0 . 5 4 7 5 4 7 2 7 8 ;and ⌊ 1 0 0 0 Q ⌋ = ⌊ 3 0 5 4 7 . 5 4 7 2 7 8 ⌋ = 3 0 5 4 7