tính nhanh : A =1/3×8+1/6×12+1/9×16+…….+1/1512×2020 15/09/2021 Bởi Alice tính nhanh : A =1/3×8+1/6×12+1/9×16+…….+1/1512×2020
Đáp án: `A =1/3×8+1/6×12+1/9×16+…….+1/1512×2020` `⇒A=1/5.(1/3-1/8+1/6-1/12+1/9-1/12+…+1/1512-1/2020)` `⇒A=1/5.(1/3-1/2020)` `⇒A=1/5`.`2017/6060` `⇒A=2017/30300` Vậy A=$\frac{2017}{30300}$ Bình luận
Đáp án: Giải thích các bước giải: $A$ = $\dfrac{1}{3.8}$ + $\dfrac{1}{6.12}$ + $\dfrac{1}{9.16}$ … + $\dfrac{1}{1512.2020}$ $A$ = $\dfrac{1}{5}$ x ( $\dfrac{1}{3}$-$\dfrac{1}{8}$ + $\dfrac{1}{6}$ – $\dfrac{1}{12}$ + … + $\dfrac{1}{1512}$ – $\dfrac{1}{2020}$ ) $A$ = $\dfrac{1}{5}$ x ( $\dfrac{1}{3}$ – $\dfrac{1}{2020}$ ) $A$ = $\dfrac{1}{5}$ x $\dfrac{2017}{6060}$ $A$ = $\dfrac{2017}{30300}$ Bình luận
Đáp án:
`A =1/3×8+1/6×12+1/9×16+…….+1/1512×2020`
`⇒A=1/5.(1/3-1/8+1/6-1/12+1/9-1/12+…+1/1512-1/2020)`
`⇒A=1/5.(1/3-1/2020)`
`⇒A=1/5`.`2017/6060`
`⇒A=2017/30300`
Vậy A=$\frac{2017}{30300}$
Đáp án:
Giải thích các bước giải:
$A$ = $\dfrac{1}{3.8}$ + $\dfrac{1}{6.12}$ + $\dfrac{1}{9.16}$ … + $\dfrac{1}{1512.2020}$
$A$ = $\dfrac{1}{5}$ x ( $\dfrac{1}{3}$-$\dfrac{1}{8}$ + $\dfrac{1}{6}$ – $\dfrac{1}{12}$ + … + $\dfrac{1}{1512}$ – $\dfrac{1}{2020}$ )
$A$ = $\dfrac{1}{5}$ x ( $\dfrac{1}{3}$ – $\dfrac{1}{2020}$ )
$A$ = $\dfrac{1}{5}$ x $\dfrac{2017}{6060}$
$A$ = $\dfrac{2017}{30300}$