Cho A = 1/4 ²+1/5 ² + 1/6 ² +…+1/10² CM A< 7/44 01/11/2021 Bởi Arya Cho A = 1/4 ²+1/5 ² + 1/6 ² +…+1/10² CM A< 7/44
`A = 1/(4 ²)+1/(5 ²) + 1/(6 ²) +…+1/(10²)` `A=1/(4.4)+1/(5.5)+…+1/(10.10)` `A<1/(4.5)+1/(5.6)+…+1/(10.11)` `A<1/4-1/5+1/5-1/6+…+1/10-1/11` `A<1/4-1/11` `A<7/44` Bình luận
Đáp án: Giải thích các bước giải: `A<1/3.5+1/4.6+1/5.7+1/6.8+1/7.9+1/8.10+1/9.11` `A<1/2(2/3.5+2/5.7+2/7.9+2/9.11)+1/2(2/4.6+2/6.8+2/8.10)` `A<1/2(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)+1/2(1/2-1/4+1/4-1/6+1/6-1/8+1/8-1/10)` `A<1/2(1/3-1/11)+1/2(1/2-1/10)` `A<1/2×8/33+1/2×2/5` `A<4/33+1/5=53/165<7/44(đpcm)` Chúc bn học tốt Bình luận
`A = 1/(4 ²)+1/(5 ²) + 1/(6 ²) +…+1/(10²)`
`A=1/(4.4)+1/(5.5)+…+1/(10.10)`
`A<1/(4.5)+1/(5.6)+…+1/(10.11)`
`A<1/4-1/5+1/5-1/6+…+1/10-1/11`
`A<1/4-1/11`
`A<7/44`
Đáp án:
Giải thích các bước giải:
`A<1/3.5+1/4.6+1/5.7+1/6.8+1/7.9+1/8.10+1/9.11`
`A<1/2(2/3.5+2/5.7+2/7.9+2/9.11)+1/2(2/4.6+2/6.8+2/8.10)`
`A<1/2(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)+1/2(1/2-1/4+1/4-1/6+1/6-1/8+1/8-1/10)`
`A<1/2(1/3-1/11)+1/2(1/2-1/10)`
`A<1/2×8/33+1/2×2/5`
`A<4/33+1/5=53/165<7/44(đpcm)`
Chúc bn học tốt