Đáp án:
`1/5+1/13+1/25+1/41+1/61+1/85+1/113<1/2`
Giải thích các bước giải:
`1/5+1/13+1/25+1/41+1/61+1/85+1/113`
`=(1/5+1/13+1/25+1/41+1/61+1/85)+1/113`
`1/2`
`=3/7+1/14`
`(1/5+1/13+1/25+1/41+1/61+1/85)-3/7`
`=-0,1924332926<0`
`=>(1/5+1/13+1/25+1/41+1/61+1/85)<3/7`
Mà `1/113<1/14`
`=>1/5+1/13+1/25+1/41+1/61+1/85+1/113<1/2`