S = 2 + 22 + 23 + 24 + ..........+22009+ 22010
S = (2 + 22) + (23 + 24) + ..........+(22009+ 22010)
S = 6 . 1 + 6 . 22 +.............+6 . 22008
S = 6. (1 + 22 +.............+22008) chia hết cho 6 ( DPCM)
S = 2 + 22 + 23 + 24 + . . . + 22009 + 22010
S = (2 + 22) + (23 + 24) + . . . + (22009 + 22010)
S= (2 + 22) + 22(2+22) +...+ 22008(2+22)
S= 6 + 22.6 +...+ 22008.6
S= 6(1+22+...+22008) chia hết cho 6
=> S = ( 2 + 22 ) + ( 23 + 24 ) + .... + ( 22009 + 22010 )
=> S = 1 . ( 2 + 22 ) + 22 ( 2 + 22 ) + .... + 22008 ( 2 + 22 )
=> S = 1. 6 + 22 . 6 + ..... + 22008 . 6
=> S = 6.( 1 + 22 + .... + 22008 )
Vì 6 ⋮ 6 => S ⋮ 6
Vậy S ⋮ 6