A = 2^100 - 2^99 - 2^98 - .... - 2^2 - 2
A . 2 = 2^101 - 2^100 - 2^99 - ... - 2^3 - 2^2
A . 2 - A = ( 2^101 - 2^100 - 2^99 - ... - 2^3 - 2^2 ) - ( 2^100 - 2^99 - 2^98 - .... - 2^2 - 2 )
A = 2 ^101 - 2^100 - 2^99 - ... - 2^3 - 2^2 - 2^100 + 2^99 + 2^98 + .... + 2^2 + 2
A = 2^101 - 2^100 - 2^100 + 2
A = 2^101 - ( 2^100 + 2^100 ) + 2
A = 2^101 - ( 2^100 . 2 ) + 2
A = 2^101 - 2^101 + 2
A = 2 ( số nguyên tố ) ( Điều phải chứng minh )
