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![](https://rs.olm.vn/images/avt/0.png?1311)
Đặt \(A=\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^8}\)
\(\Leftrightarrow\)\(3A=1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^7}\)
\(\Leftrightarrow\)\(3A-A=\left(1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^7}\right)-\left(\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^8}\right)\)
\(\Leftrightarrow\)\(2A=1-\frac{1}{3^8}\)
\(\Leftrightarrow\)\(2A=\frac{3^8-1}{3^8}\)
\(\Leftrightarrow\)\(A=\frac{3^8-1}{3^8}:2\)
\(\Leftrightarrow\)\(A=\frac{3^8-1}{3^8}.\frac{1}{2}\)
\(\Leftrightarrow\)\(A=\frac{3^8-1}{2.3^8}\)
b) Đặt \(A=\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+.....+\frac{1}{3^8}\)
\(\Rightarrow\)\(3A=1+\frac{1}{3}+\frac{1}{3^2}+....+\frac{1}{3^7}\)
\(\Rightarrow\)\(3A-A=\left(1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^7}\right)-\left(\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+....+\frac{1}{3^8}\right)\)
\(\Rightarrow\)\(2A=1-\frac{1}{3^8}\)
\(\Rightarrow\)\(A=\frac{1-\frac{1}{3^8}}{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
ket qua bang 152 , 952
minh nha
moi nguoi tk minh nha minh dang am
![](https://rs.olm.vn/images/avt/0.png?1311)
\(136.68+16.272=136.2.34+16.272\)
\(=272.34+16.272=272.\left(34+16\right)=272.50=13600\)
(k cho tớ với nhá!)
\(136\cdot68+16\cdot272=136\cdot68+16\cdot2\cdot136=136\cdot\left(68+32\right)=13600.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
136.68+16.272=136.68+16.2.136
=136.(68+16.2)
=136.100
=13600
k cho mik nha bạn
136.68+16.272
=136.68+16.2.136
=136.68+32.136
=136.(68+32)
=136.100
=13600
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a , 19 , 64 + 76 , 34 = 95 ,98
b, 35,12 + 65 ,13 = 100,25
c, 136,68 + 16 ,272 = 152 ,952
a, 19.64+76.34 = 95.98
b, 35.12+65.13 = 100,25
c, 136.68+16.272 = 152.95200
k mk nhé! Thanksssss
![](https://rs.olm.vn/images/avt/0.png?1311)
136.68+272.16
=136.68+136.2.16
=136.68+136.32
=136(68+32)
=136.100
=13600
vậy 136.68+16.272=13600
cich cho minh di
![](https://rs.olm.vn/images/avt/0.png?1311)
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\(136.68+16.272\)
\(=136.68+16.4.68\)
\(=146.68+64.68\)
\(=68.\left(136+64\right)\)
\(=68.200\)
\(=13600\)
Mọi người giúp em với ạ ! Em đang gấp lắm !