Toán Cmr: b=1/2 mũ 3+1/3 mũ 3+1/4 mũ 3+…+1/2019 mũ 3 < 1/2 26/07/2021 By Ayla Cmr: b=1/2 mũ 3+1/3 mũ 3+1/4 mũ 3+…+1/2019 mũ 3 < 1/2
Đáp án: `B<1/2` Giải thích các bước giải: `B=1/2^3+1/3^3+1/4^3+…+1/2019^3` `B=1/(2.2.2)+1/(3.3.3)+1/(4.4.4)+…+1/(2019.2019.2019)` `B<1/(1.2.3)+1/(2.3.4)+1/(3.4.5)+…+1/(2018.2019.2020)` `B<1/2(1/1.2+1/2.3+1/3.4+1/3.4+1/4.5+…+1/2018.2019+1/2019.2020)<1/2` Vậy `B<1/2`. Trả lời
Đáp án:
`B<1/2`
Giải thích các bước giải:
`B=1/2^3+1/3^3+1/4^3+…+1/2019^3`
`B=1/(2.2.2)+1/(3.3.3)+1/(4.4.4)+…+1/(2019.2019.2019)`
`B<1/(1.2.3)+1/(2.3.4)+1/(3.4.5)+…+1/(2018.2019.2020)`
`B<1/2(1/1.2+1/2.3+1/3.4+1/3.4+1/4.5+…+1/2018.2019+1/2019.2020)<1/2`
Vậy `B<1/2`.