CMR A=1/2-2/2^2+3/2^3-4/2^4+….+99/2^99-100/2^100<2/9 10/11/2021 Bởi Hadley CMR A=1/2-2/2^2+3/2^3-4/2^4+….+99/2^99-100/2^100<2/9
`A=1/2-2/2^2+3/2^3-4/2^4+….+99/2^99-100/2^100<2/9` `A=1/2-2/4+3/6-4/8+….+………..<2/9` `A=1/2-1/2+1/2-1/2+……+……….<2/9` `A=0-0+0-0+…..+………..<2/9` `⇒A<2/9` Bình luận
Đáp án:
Giải thích các bước giải:
`A=1/2-2/2^2+3/2^3-4/2^4+….+99/2^99-100/2^100<2/9`
`A=1/2-2/4+3/6-4/8+….+………..<2/9`
`A=1/2-1/2+1/2-1/2+……+……….<2/9`
`A=0-0+0-0+…..+………..<2/9`
`⇒A<2/9`