Question

S=3/5.7+3/7.9+...+3/59.61

Answer 1

Giải:

S=3/5.7+3/7.9+...+3/59.61

S=3/2.(2/5.7+2/5.7+...+2/59.61)

S=3/2.(1/5-1/7+1/7-1/9+...+1/59-1/61)

S=3/2.(1/5-1/61)

S=3/2.56/305

S=84/305

Chúc bạn học tốt!

Answer 2

Answer 3

`S=3/(5.7)+3/(7.9)+....+3/(59.61)`

`=>2S=3(2/(5.7)+2/(7.9)+....+2/(59.61))`

`=>2S=3(1/5-1/7+.....+1/59-1/61)`

`=>2S=3(1/5-1/61)=168/305`

`=>S=84/305`