Question

S= 2 la 1+ 2 la 2+ 2 la 3+....+ 2 la 120

Answer 1

$S=2^{1} +2^{2}+2^{3}+...+2^{120}$            x2
$2S=2^{2}+2^{3}+...+2^{121} +2-2$
$2S=S+2^{121} -2$
$S=2^{121} -2=2( 2^{120}-1)$