A = 1+2+22+23+...........+2100
=>2A = 2+22+23+24+..............+2101
=> 2A - A = 2101-1
=> A = 2101 - 1
A=1+2+2^2+2^3+...+2^100
=>2A-A=(2+2^2+2^3+2^4+...+2^101)-(1+2+2^2+2^3+...+2^100)
=>2A-A=2^101-1
hay A=2^101-1
=>2A=2+22+23+24+.........+2101
=>2A-A=(2+22+23+24+....+2101)-(1+2+22+23+........+2100)
=>A=2101-1+2100