C=2/3+2/6+2/12+2/24+2/48+2/96+2/192
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
127/96 nhé
nếu sai bạn sửa cho mình nhé
thank you
mình cảm ơn trước
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{2}{3}+\dfrac{2}{6}+\dfrac{2}{12}+\dfrac{2}{24}+\dfrac{2}{48}+\dfrac{2}{96}+\dfrac{2}{192}\)
= \(2\left(\dfrac{1}{3}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{24}+\dfrac{1}{48}+\dfrac{1}{96}+\dfrac{1}{192}\right)\)
= \(2\left(\dfrac{1}{1.3}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.6}+\dfrac{1}{6.8}+\dfrac{1}{8.12}+\dfrac{1}{12.16}\right)\)
= \(\dfrac{2}{3}+2\left(\dfrac{1}{2}-\dfrac{1}{4}\right)+2\left(\dfrac{2}{4.6}+\dfrac{2}{6.8}\right):2+\dfrac{1}{2}\left(\dfrac{4}{8.12}+\dfrac{4}{12.16}\right)\)
= \(\dfrac{2}{3}+\dfrac{1}{2}+\dfrac{1}{8}+\dfrac{1}{32}\)
= \(\dfrac{127}{96}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Đặt BT trên là A
\(2A=\frac{4}{3}+\frac{2}{3}+\frac{2}{6}+\frac{2}{12}+\frac{2}{24}+\frac{2}{48}+\frac{2}{96}\)
\(A=2A-A=\frac{4}{3}-\frac{2}{192}=\frac{127}{192}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{2}{3}+\dfrac{2}{6}+\dfrac{2}{12}+\dfrac{2}{24}+\dfrac{2}{48}+\dfrac{2}{96}+\dfrac{2}{192}\\ =\dfrac{128}{192}+\dfrac{64}{192}+\dfrac{32}{192}+\dfrac{16}{192}+\dfrac{8}{192}+\dfrac{4}{192}+\dfrac{2}{192}\\ =\dfrac{128+64+32+16+8+4+2}{192}\\ =\dfrac{254}{192}=\dfrac{127}{96}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
`a)-2/3-2/6+2/12+2/24+2/48+2/96+2/192`
`=-4/6-2/6+1/6+1/12+1/24+1/48+1/96`
`=-5/6+1/12+1/24+1/48+1/96`
`=-10/12+1/12+1/24+1/48+1/96`
`=-9/12+1/24+1/48+1/96`
`=-18/24+1/24+1/48+1/96`
`=-17/24+1/48+1/96`
`=-34/48+1/48+1/96`
`=-33/48+1/96`
`=-66/96+1/96=-65/96`