Question

Calculati: 2+2^2+2^3+...+2^9

Answer 1

Adunăm și scădem 2

2+2+2^2+2^3+...+2^9-2=

=4+2^2+2^3+...+2^9-2=

=2^2+2^2+2^3+...+2^9-2=

=2*2^2+2^3+...+2^9-2=

2^3+2^3+...2^9-2=

2*2^3+...+2^9-2=

2^4+...+2^9-2=

.

.

=2*2^9-2=

=2^10-2=

=1024-2=

=1022