tinh nhanh A= 1/3+1/6+1/12+1/24+1/48+1/96
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2
0
S
23 tháng 2 2017
\(\frac{1}{3}+\frac{1}{6}+\frac{1}{12}+\frac{1}{24}+\frac{1}{48}+\frac{1}{96}\)
\(=\frac{1}{2}+\frac{1}{8}+\frac{1}{32}\)
\(=\frac{5}{8}+\frac{1}{32}\)
\(=\frac{21}{32}\)
LL
1
TN
8 tháng 5 2016
\(=2\left(\frac{1}{3}+\frac{1}{6}+...+\frac{1}{192}\right)\)
\(=2\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{6}+...+\frac{1}{96}-\frac{1}{192}\right)\)
\(=2\left(1-\frac{1}{192}\right)\)
\(=2\times\frac{191}{192}\)
\(=\frac{191}{96}\)
TP
2
VD
1
DT
7
24 tháng 7 2018
\(\frac{1}{3}+\frac{1}{6}+\frac{1}{12}+\frac{1}{24}+\frac{1}{48}+\frac{1}{96}\)
\(=\left(\frac{1}{3}+\frac{1}{6}\right)+\left(\frac{1}{12}+\frac{1}{24}\right)+\left(\frac{1}{48}+\frac{1}{96}\right)\)
\(=\frac{1}{2}+\frac{1}{8}+\frac{1}{32}\)
\(=\frac{21}{32}\)
\(A=\frac{1}{3}+\frac{1}{6}+\frac{1}{12}+\frac{1}{24}+\frac{1}{48}+\frac{1}{96}\)
\(\Rightarrow3A=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\)
\(\Rightarrow3A=1+1-\frac{1}{2}+\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{8}+\frac{1}{8}-\frac{1}{16}+\frac{1}{16}-\frac{1}{32}\)
\(\Rightarrow3A=1+1-\frac{1}{32}\)
\(\Rightarrow3A=2-\frac{1}{32}\)
\(\Rightarrow A=\left(2-\frac{1}{32}\right):3=\frac{21}{32}\)
P/s : Đúng nha
A= 1/3+1/3-1/6+1/6-1/12+1/12-1/24+1/24-1/48+1/48-1/96
A=1/3+1/3-1/96
A=2/3-1/96
A=63/32.