Bạn tham khảo :
$A = 1 + 2 +2^2 + 2^3 + ..... + 2^{200}$
$2A = 2( 1 + 2 +2^2 + 2^3 + ..... + 2^{200} )$
$2A = 2+2^2 + 2^3 + 2^4 + ...+ 2^{201}$
$2A-A = (2+2^2 + 2^3 + 2^4 + ...+ 2^{201}) - (1 + 2 +2^2 + 2^3 + ..... + 2^{200})$
$A = ( 2-2) + (2^2-2^2) + (2^3 - 2^3) + (2^4 - 2^4) +...+ (2^{201} -1)$
$A = 2^{201} -1$
Mà $A = 2^{201} -1$
⇒ $A + 1 = 2^{201}$