Giải thích các bước giải:
`3+ 3/5+3/25+3/125+3/625`
`=3+ 3/5+3/5^2+3/5^3+3/5^4`
`=3(1+ 1/5+1/5^2+1/5^3+1/5^4)`
Đặt `A=1+ 1/5+1/5^2+1/5^3+1/5^4`
`=>5A=5+ 1+1/5+1/5^2+1/5^3`
`=>5A-A=(5+ 1+1/5+1/5^2+1/5^3)-(1+ 1/5+1/5^2+1/5^3+1/5^4)`
`=>4A=5-1/5^4`
`=>4A=(5^5-1)/5^4`
`=>A=(5^5-1)/4.5^4`
`=>3+ 3/5+3/25+3/125+3/625`
`=3.(5^5-1)/4.5^4`
`=3. 781/625`
`=2343/625`