Đáp án:
`c)1`
Giải thích các bước giải:
Sửa đề:`c)(1/9-1/7-1/11)/(4/9-4/7-4/11)+(3/5-3/25-3/125-3/165)/(4/5-4/25-4/125-4/625)`
`→`c)(1/9-1/7-1/11)/(4/9-4/7-4/11)+(3/5-3/25-3/125-3/625)/(4/5-4/25-4/125-4/625)`
`c)(1/9-1/7-1/11)/(4/9-4/7-4/11)+(3/5-3/25-3/125-3/625)/(4/5-4/25-4/125-4/625)`
`=(1/9-1/7-1/11)/(4(1/9-1/7-1/11))+(3(1/5-1/25-1/125-1/625))/(4(1/5-1/25-1/125-1/625))`
`=1/4+3/4`
`=4/4`
`=1`
