Đáp án + Giải thích các bước giải:
`B=1/160-4/40.43-4/43.46-...-4/157.160`
`=>B=1/160-(4/40.43+4/43.46+...+4/157.160)`
`=>B=1/160-4/3(3/40.43+3/43.46+...+3/157.160)`
`=>B=1/160-4/3(1/40-1/43+1/43-1/46+...+1/157-1/160)`
`=>B=1/160-4/3(1/40-1/160)`
`=>B=1/160-4/3(4/160-1/160)`
`=>B=1/160-4/3 . 3/160`
`=>B=1/160-1/40`
`=>B=1/160-4/160`
`=>B=-3/160`
Vậy `B=-3/160`