Đáp án:
`2047/1024`
Giải thích các bước giải:
Cho `A=1+1/2+1/4+1/8+...+1/1024`
`2A=2(1+1/2+1/4+1/8+...+1/1024)`
`2A=2+ 2.1/2 + 2.1/4 + 2.1/8+....+2.1/1024`
`2A=2+1+1/2+1/4+1/8+...+1/512`
`2A - A= (2+1+1/2+1/4+1/8+...+1/512)-(1+1/2+1/4+1/8+...+1/1024)`
`A=2- 1/1024 = 2047/1024`