Đáp án:
`3/(1xx4)+3/(4xx7)+3/(7xx10)+3/(10xx13)+...+3/(46xx49)+3/(49xx52)=51/52`
Giải thích các bước giải:
`3/(1xx4)+3/(4xx7)+3/(7xx10)+3/(10xx13)+...+3/(46xx49)+3/(49xx52)`
`=1/1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+...+1/46-1/49+1/49-1/52`
`=1/1+(1/4-1/4)+(1/7-1/7)+(1/10-1/10)+...+(1/46-1/46)+(1/49-1/49)-1/52`
`=1/1-1/52`
`=52/52-1/52`
`=51/52`