Cho A= 1/5+1/6+1/7+1/8+1/9.So sánh A với 1 30/08/2021 Bởi Cora Cho A= 1/5+1/6+1/7+1/8+1/9.So sánh A với 1
`A= 1/5+1/6+1/7+1/8+1/9`Ta thấy :`1/5 =1/5``1/6 <1/5``1/7 < 1/5``1/8 < 1/5``1/9 <1/5``=> 1/5+1/6+1/7+1/8+1/9 < 1/5 + 1/5 + 1/5 + 1/5 + 1/5``=> A < 1/5. 5``=> A <1` Vậy `A<1` Bình luận
Ta có: A=1/5+1/6+1/7+1/8+1/9 Mà A= 1/6<1/5, 1/7<1/5, 1/8<1/5, 1/9<1/5 Suy ra: A<1/5+1/5+1/5+1/5+1/5 Suy ra: A<1/5.5 Suy ra: A<1 Bình luận
`A= 1/5+1/6+1/7+1/8+1/9`
Ta thấy :
`1/5 =1/5`
`1/6 <1/5`
`1/7 < 1/5`
`1/8 < 1/5`
`1/9 <1/5`
`=> 1/5+1/6+1/7+1/8+1/9 < 1/5 + 1/5 + 1/5 + 1/5 + 1/5`
`=> A < 1/5. 5`
`=> A <1`
Vậy `A<1`
Ta có: A=1/5+1/6+1/7+1/8+1/9
Mà A= 1/6<1/5, 1/7<1/5, 1/8<1/5, 1/9<1/5
Suy ra: A<1/5+1/5+1/5+1/5+1/5
Suy ra: A<1/5.5
Suy ra: A<1