Toán D= 4/2×4 + 4/4×6 + 4/6×8 + …… + 4/2018×2020 12/09/2021 By Harper D= 4/2×4 + 4/4×6 + 4/6×8 + …… + 4/2018×2020
`D=4/(2×4)+4/(4×6)+4/(6×8)+…+4/(2018×2020)` `⇒D=2.(2/(2×4)+2/(4×6)+2/(6×8)+…+2/(2018×2020))` `⇒D=2.(1/2-1/4+1/4-1/6+1/6-1/8+…+1/(2018)-1/(2020))` `⇒D=2.(1/2-1/(2020))` `⇒D=2.(1009)/(2020)` `⇒D=(1009)/(1010)` Vậy `D=(1009)/(1010)`. Trả lời
Đáp án:
Giải thích các bước giải:
`D=4/(2×4)+4/(4×6)+4/(6×8)+…+4/(2018×2020)`
`⇒D=2.(2/(2×4)+2/(4×6)+2/(6×8)+…+2/(2018×2020))`
`⇒D=2.(1/2-1/4+1/4-1/6+1/6-1/8+…+1/(2018)-1/(2020))`
`⇒D=2.(1/2-1/(2020))`
`⇒D=2.(1009)/(2020)`
`⇒D=(1009)/(1010)`
Vậy `D=(1009)/(1010)`.