Toán giải hộ mình câu này : 2/6+2/12+2/20+…=2/X.(X+1) 09/07/2021 By Brielle giải hộ mình câu này : 2/6+2/12+2/20+…=2/X.(X+1)
Đáp án: `2/6+2/12+2/20+….+2/(x(x+1))` `=2(1/6+1/12+1/20+….+2/(x(x+1)))` `=2(1/6+1/12+1/20+….+1/(x(x+1)))` `=2(1/(2.3)+1/(3.4)+1/(4.5)+…+1/x-1/(x+1))` `=2(1/2-1/3+1/3-1/4+1/4-1/5+….+1/x-1/(x+1))` `=2(1/2-1/(x+1))` `=2((x+1-2)/(2(x+1)))` `=2*(x-1)/(2(x+1))` `=(x-1)/(x+1)` Trả lời
`2/6+2/12+2/20+…+2/(x.(x+1))` `=> 2/(2.3)+2/(3.4)+2/(4.5)+…+2/(x.(x+1))` `=> 2 . (1/(2.3)+1/(3.4)+1/(4.5)+…+1/(x.(x+1)))` `=> 2 . (1/2 – 1/3 + 1/3 – 1/4 + 1/4 – 1/5 + ….+ 1/x – 1/(x+1))` `=> 2 . (1/2 -1/(x+1))` (Chúc bạn học tốt) Trả lời
Đáp án:
`2/6+2/12+2/20+….+2/(x(x+1))`
`=2(1/6+1/12+1/20+….+2/(x(x+1)))`
`=2(1/6+1/12+1/20+….+1/(x(x+1)))`
`=2(1/(2.3)+1/(3.4)+1/(4.5)+…+1/x-1/(x+1))`
`=2(1/2-1/3+1/3-1/4+1/4-1/5+….+1/x-1/(x+1))`
`=2(1/2-1/(x+1))`
`=2((x+1-2)/(2(x+1)))`
`=2*(x-1)/(2(x+1))`
`=(x-1)/(x+1)`
`2/6+2/12+2/20+…+2/(x.(x+1))`
`=> 2/(2.3)+2/(3.4)+2/(4.5)+…+2/(x.(x+1))`
`=> 2 . (1/(2.3)+1/(3.4)+1/(4.5)+…+1/(x.(x+1)))`
`=> 2 . (1/2 – 1/3 + 1/3 – 1/4 + 1/4 – 1/5 + ….+ 1/x – 1/(x+1))`
`=> 2 . (1/2 -1/(x+1))`
(Chúc bạn học tốt)