Đáp án:
`=50/101`
Giải thích các bước giải:
`1/1.3+1/3.5+1/5.7+ ..+1/99.101`
`=(1.2/1.3+1.2/3.5+1.2/5.7+ ..+1.2/99.101):2`
`=(2/1.3+2/3.5+2/5.7+ ..+2/99.101). 1/2`
`=(1-1/3+1/3-1/5+1/5-1/7+...+1/99-1/101). 1/2`
`=(1-1/101). 1/2`
`=(101/101-1/101). 1/2`
`=100/101. 1/2`
`=50/101`