Đáp án:
Giải thích các bước giải:
`1/2 + 1/4 + 1/8 + 1/16 + ......... + 1/256 + 1/512`
Đặt `A = 1/2 + 1/4 + 1/8 + 1/16 + ........... + 1/256 + 1/512`
`2A = 1 + 1/2 + 1/4 + 1/8 + .............. + 1/128 + 1/256`
`2A - A = ( 1 + 1/2 + 1/4 +1/8 + ............. +1/128 + 1/256) - (1/2 + 1/4 + 1/8 + ........... + 1/256 + 1/512)`
`2A - A =1 + 1/2 + 1/4+ 1/8 + ........ +1/128 + 1/256 - 1/2 - 1/4 - 1/8 - .............. -1/256 - 1/512`
`2A - A = 1 + (1/2 - 1/2) + (1/4 - 1/4) + (1/8 - 1/8) + ...................+ (1/256 - 1/256) + 1/512`
`A =1 - 1/512 = 511/512`
`text{ @toanisthebest}`