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a ) x x 1 x 1 x 0 Dk : x 1 x x x x (1 x) x2 x2 x 1 x x 0 x x x2 b) 0 x 12 x TH 1: x 0 x 12 x x 0 x 1* 3x 12 x x Từ * ** ta có 6 39 x 39 ** 39 TH : x 0 x 12 x x 0 x 1*** 3x 12 x x x Từ *** **** 6 39 6 39 ****