A=2021/2+2021/6+2021/12+…+2021/9702+2021/9900 04/08/2021 Bởi Harper A=2021/2+2021/6+2021/12+…+2021/9702+2021/9900
`A=2021/2+2021/6+2021/12+…+2021/9702+2021/9900``A=2021(1/2+1/6+1/12+…+1/9702+1/9900)``A=2021(1/1.2+1/2.3+1/3.4+…+1/98.99+1/99.100)``A=2021(1-1/2+1/2-1/3+1/3-1/4+…+1/98-1/99+1/99-1/100)``A=2021(100/100-1/100)``A=2021.99/100``A=200079/100` Áp dụng công thức:`1/[n.(n+1)]=1/n-1/[n+1]` Bình luận
`A= 2021/2 + 2021/6 + 2021/12 +…+ 2021/9900` `A= 2021( 1/2 + 1/6+ 1/12 +… + 1/9900)` `A= 2021( 1/1.2 + 1/2.3 + 1/3.4 +…+ 1/99.100)` `A= 2021( 1/1 – 1/2 + 1/2 – 1/3 +…+ 1/99- 1/100)` `A= 2021( 1 – 1/100)` `A = 2021 . 99/100` `A=200079/100` Vậy `A=200079/100` Bình luận
`A=2021/2+2021/6+2021/12+…+2021/9702+2021/9900`
`A=2021(1/2+1/6+1/12+…+1/9702+1/9900)`
`A=2021(1/1.2+1/2.3+1/3.4+…+1/98.99+1/99.100)`
`A=2021(1-1/2+1/2-1/3+1/3-1/4+…+1/98-1/99+1/99-1/100)`
`A=2021(100/100-1/100)`
`A=2021.99/100`
`A=200079/100`
Áp dụng công thức:`1/[n.(n+1)]=1/n-1/[n+1]`
`A= 2021/2 + 2021/6 + 2021/12 +…+ 2021/9900`
`A= 2021( 1/2 + 1/6+ 1/12 +… + 1/9900)`
`A= 2021( 1/1.2 + 1/2.3 + 1/3.4 +…+ 1/99.100)`
`A= 2021( 1/1 – 1/2 + 1/2 – 1/3 +…+ 1/99- 1/100)`
`A= 2021( 1 – 1/100)`
`A = 2021 . 99/100`
`A=200079/100`
Vậy `A=200079/100`