... + 10 n + + 1) = 4 (10 2n n n B = 2.888 = 16.111 1 = 16 (10 + 10 + + 1) Cõu 3: T gi thit ta cú T ú suy D=A+2B+4= 9D = n n 4 (102 n + 102 n + + 1) + 16(10n + 10n + + 1) +4 4 (10 1) (102 n + 102 ... + y = x + y = x = 2, 102 x 101 y 102 x + 101 y = 507, y = 2,8 100 + 100 = 5, 072 Vy s dõn ca tnh A v B nm 101 3 l: 2,2 triu ngi 102 100 = 2,244 triu ngi v 2,8 101 100 x, y = 2,8281 Bi A a) ... + + 1) +4 4 (10 1) (102 n + 102 n + + 1) + 16 (10 1) (10 n + 10 n + + 1) + 36 4 (102 n 1) + 16(10n 1) + 36 = 4 (102 n + 4.10n + 4) 9D= = ( 10n + ) Suy pcm Cõu 5: Vi gt ó cho ta cú: a a...