1/1+2 + 1/2+3 + 1/ 3+4 + …… 1/2019+2020 = …. , giúp em với ạ , mai nộp bài rùi .
1/1+2 + 1/2+3 + 1/ 3+4 + …… 1/2019+2020 = …. , giúp em với ạ , mai nộp bài rùi .
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1/1+2 + 1/2+3 + 1/ 3+4 + …… 1/2019+2020 = …. , giúp em với ạ , mai nộp bài rùi .
Hưng Khoa
`1/1.2` + `1/2.3` + `1/ 3.4` + …… +`1/2019.2020 `
= 1 – `1/2` + `1/2` – `1/3` + ………+ `1/2019` – `1/2020`
= 1 – `1/2020`
= `2020/2020` – `1/2020`
= `1019/2020`
XIN HAY NHẤT
Euphemia
`1/(1.2)` + `1/(2.3)` + `1/( 3.4)` + …… +`1/(2019.2020) `
= `1 – 1/2 + 1/2 – 1/3 + ………+ 1/2019 – 1/2020`
= `1 – 1/2020`
= `2020/2020 – 1/2020`
= `2019/2020`