Question

2+2^2+2^3+...+2^50

Answer 1

S=2+2^2+2^3+...+2^50 

2S= 2^2+2^3+...+2^51

=>2S - S = ( 2^2+2^3+...+2^51 ) - ( 2+2^2+2^3+...+2^50 )

= 2^51-2

Answer 2

S=2+2^2+2^3+...+2^50 

2S= 2^2+2^3+...+2^51

=>2S - S = ( 2^2+2^3+...+2^51 ) - ( 2+2^2+2^3+...+2^50 )

= 2^51-2