... = 20 29099 - 20 10 .20 11 = 20 29099 20 10 .20 11 20 11x = 20 29099 20 10 .20 11 : 20 11 = x = 20 29099 20 11x + 0,50 0,50 0,50 0 ,25 0 ,25 0 ,25 0 ,25 0 ,25 0 ,25 0 ,25 0 ,25 b/ - 2( 1 + + + + x) = 21 0 0 ,25 ... - ca Cú: + 52 + 53 + 54 + 55 + 56 = 5(1 + 53) + 52( 1 + 53) + 53(1 + 53) = 126 + 52. 126 + 53. 126 + 52 + 53 + 54 + 55 + 56 chia ht cho 126 S = (5 + 52 + 53 + 54 + 55 + 56) + 56(5 + 52 + 53 + 54 ... + + + x) = 21 0 0 ,25 - 0 ,25 x( x + 1) = 21 0 x( x + 1) = 21 0 - Gii c x = 14 (Do 21 0 = 2. 3.5.7 = 14.15) 0 ,25 0 ,25 c/ 3x+3x+1+3x +2= 351 3x+3x 3+3x 32= 351 3x(1+3+9)=351 3x =27 =33 x=3 Cõu 3: (1.0 im)...