... => 77 677 6 + 77 777 7 + 77 877 8 ≡ - 377 7 + 377 8 (mod 5) Hay 77 677 6 + 77 777 7 + 77 877 8 ≡ + 3. 377 7 - 377 7 (mod 5) 77 677 6 + 77 777 7 + 77 877 8 ≡ + 377 7(3 - 1) (mod 5) 77 677 6 + 77 777 7 + 77 877 8 ≡ + 2. 377 7... 3) 77 8 ≡ (mod 3) => 77 877 8≡ (mod 3) => 77 677 6 + 77 777 7 + 77 877 8 chia cho dư +Ta có 77 6 ≡ (mod 5) => 77 677 6 ≡ (mod 5) 77 7 ≡ - (mod 5) => 77 777 7 ≡ - 377 7 (mod 5) 77 8 ≡ (mod 5) => 77 877 8 ≡ 377 8... => 570 + 75 0 chia cho 12 dư Bài : Tìm số dư A = 77 677 6 + 77 777 7 + 77 877 8 chia cho chia cho 5? Giải : 77 6 +Ta có 77 6 ≡ - 1(mod 3) => 77 6 ≡ -1 (mod 3) => 77 677 6 ≡ (mod 3) 77 7 ≡ (mod 3) => 77 777 7 ≡