1bb12bb23bb34bb45bb56bb67bb78bb89bb9Trong đó b=0;1;2;3;4;5;6;7;8;9Ta có công thức ( 1001+2002+3003+4004+5005+6006+7007+8008+9009)x (000+110+220+330+440+550+660+770+880+990) =
1bb12bb23bb34bb45bb56bb67bb78bb89bb9Trong đó b=0;1;2;3;4;5;6;7;8;9Ta có công thức ( 1001+2002+3003+4004+5005+6006+7007+8008+9009)+ (000+110+220+330+440+550+660+770+880+990) x9=