Question

1/50+1/10+1/20+..........+1/640+1/1280

Answer 1

cứu với ạ

Answer 2

Sửa đê: A=1/5+1/10+...+1/640+1/1280

=1/5(1+1/2+...+1/128+1/256)

Đặt B=1+1/2+...+1/128+1/256

=>2B=2+1+...+1/64+1/128

=>B=2-1/256=511/256

=>A=511/1280