Bài 3: Tìm x
`x – 1/1.2 – 1/2.3 – 1/3.4 – … – 1/7.8 – 1/8.9 = 1/10 + 1/9.10`
Bài 4: Cho `S = 1/11 + 1/12 + 1/13 + 1/14 + 1/15 + 1/16 + 1/17 + 1/18 + 1/19 + 1/20`
Hãy so sánh `S` với `1/2`
Bài 3: Tìm x `x – 1/1.2 – 1/2.3 – 1/3.4 – … – 1/7.8 – 1/8.9 = 1/10 + 1/9.10` Bài 4: Cho `S = 1/11 + 1/12 + 1/13 + 1/14 + 1/15 + 1/16 + 1/17 + 1/18 +
By Everleigh
Đáp án:
Bài 3:
x – 1/1.2 – 1/2.3 – 1/3.4 – …- 1/8.9 = 1/10 + 1/9.10
x – 1-1/2 – 1/2-1/3 – 1/3-1/4 – ….- 1/8- 1/9 = 1/10 + 1/9-1/10
x – 1-1/9= 1/9
x -1= 1/9+1/9 = 2/9
x= 2/9+1
x= 11/9
Bài 4 mình chưa giải kịp ‘^’