5. Tính 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90 01/08/2021 Bởi Eliza 5. Tính 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90
Đáp án: `1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90=9/10` Giải thích các bước giải: `1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90``=1/1.2+1/2.3+1/3.4+1/4.5+1/5.6+1/6.7+1/7.8+1/8.9+1/9.10``=1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10``=1/1-1/10``=10/10-1/10``=9/10`Vậy `1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90=9/10` Bình luận
`1/2` + `1/6` + `1/12` + `1/20` + `1/30` + `1/42` + `1/56` + `1/72` + `1/90` = `1/(1*2)` + `1/(2*3)` +…+ `1/(9*10)` = `1/1` – `1/2` + `1/2` – `1/3` + … + `1/9` – `1/10` = `1/1` – `1/10` = `9/10` Xin hay nhất ạ Bình luận
Đáp án:
`1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90=9/10`
Giải thích các bước giải:
`1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90`
`=1/1.2+1/2.3+1/3.4+1/4.5+1/5.6+1/6.7+1/7.8+1/8.9+1/9.10`
`=1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10`
`=1/1-1/10`
`=10/10-1/10`
`=9/10`
Vậy `1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90=9/10`
`1/2` + `1/6` + `1/12` + `1/20` + `1/30` + `1/42` + `1/56` + `1/72` + `1/90`
= `1/(1*2)` + `1/(2*3)` +…+ `1/(9*10)`
= `1/1` – `1/2` + `1/2` – `1/3` + … + `1/9` – `1/10`
= `1/1` – `1/10`
= `9/10`
Xin hay nhất ạ