\(7/9:(2+3/4x)+5/9=23/27\)
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NN
24 tháng 7 2016
\(\frac{7}{9}:\left(1+\frac{3}{4}x\right)+\frac{5}{9}=\frac{23}{27}\)
\(\frac{7}{9}:\left(1+\frac{3}{4}x\right)=\frac{8}{27}\)
\(\left(1+\frac{3}{4}x\right)=\frac{21}{8}\)
\(\frac{3}{4}x=\frac{13}{8}\)
\(x=\frac{13}{8}:\frac{3}{4}\)
\(x=\frac{13}{6}\)
Vậy \(x=\frac{13}{6}\)
24 tháng 7 2016
\(\frac{7}{9}:\left(2+\frac{3}{4}x\right)+\frac{5}{9}=\frac{23}{27}\)
\(\frac{7}{9}:\left(2+\frac{3}{4}x\right)=\frac{23}{27}-\frac{5}{9}\)
\(2+\frac{3}{4}x=\frac{7}{9}:\frac{8}{27}=\frac{21}{8}\)
\(\frac{3}{4}x=\frac{21}{8}-2=\frac{5}{8}\)
\(x=\frac{5}{8}:\frac{3}{4}=\frac{5}{6}\)
Vậy x=5/6
TN
22 tháng 7 2016
1)C= 1/5+1/10+1/20+1/40+...+1/1280
\(=\frac{1}{5}\left(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^8}\right)\)
Đặt cái trong ngoặc là A ta có:\(2A=2+1+...+\frac{1}{2^7}\)
\(2A-A=\left(2+1+...+\frac{1}{2^7}\right)-\left(1+\frac{1}{2}+...+\frac{1}{2^8}\right)\)
\(A=2-\frac{1}{2^8}\).Thay A vào ta được:\(C=\frac{1}{5}\left(2-\frac{1}{2^8}\right)=\frac{1}{5}\cdot\frac{511}{256}=\frac{511}{1280}\)
2)D= 2/1*3+2/3*5+2/5*10+2/7*9+2/9*11+2/11*18+2/13*15
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{13}-\frac{1}{15}\)
\(=1-\frac{1}{15}\)
\(=\frac{14}{15}\)
3)E= 4/3*7+4/7*11+4/11*15+4/15*19+4/19*23+4/23*27
\(=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{23}-\frac{1}{27}\)
\(=\frac{1}{3}-\frac{1}{27}\)
\(=\frac{8}{27}\)
4)G= 1/2+1/6+1/12+1/20+1/30+1/42+...+1/110
\(=\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{10.11}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{10}-\frac{1}{11}\)
\(=1-\frac{1}{11}\)
\(=\frac{10}{11}\)
5)H= 3/1*2+3/2*3+3/3*4+3/4*5+...+3/9*10
\(=3\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(=3\left(1-\frac{1}{10}\right)\)
\(=3\times\frac{9}{10}\)
\(=\frac{27}{10}\).Lần sau bạn đăng ít một thôi nhé
18 tháng 5 2018
\(\frac{7}{9}:\left(2+\frac{3}{4}.x\right)+\frac{5}{9}=\frac{23}{27}\)
\(\frac{7}{9}:\left(2+\frac{3}{4}.x\right)=\frac{23}{27}-\frac{5}{9}\)
\(\frac{7}{9}:\left(2+\frac{3}{4}.x\right)=\frac{8}{27}\)
\(2+\frac{3}{4}.x=\frac{7}{9}:\frac{8}{27}\)
\(2+\frac{3}{4}.x=\frac{21}{8}\)
\(\frac{3}{4}.x=\frac{21}{8}-2\)
\(\frac{3}{4}.x=\frac{5}{8}\)
\(x=\frac{5}{8}:\frac{3}{4}\)
\(x=\frac{5}{6}\)
18 tháng 5 2018
\(\frac{7}{9}:\left(\frac{2+3}{4x}\right)+\frac{5}{9}=\frac{23}{27}\)
\(\Leftrightarrow\frac{7}{9}:\frac{5}{4x}=\frac{23}{27}-\frac{5}{9}\)
\(\Leftrightarrow\frac{7}{9}:\frac{5}{4x}=\frac{8}{27}\)
\(\Leftrightarrow\frac{5}{4x}=\frac{7}{9}:\frac{8}{27}\)
\(\Leftrightarrow\frac{5}{4x}=\frac{21}{8}\)
\(\Leftrightarrow4x=\frac{5.8}{21}\)
\(\Leftrightarrow4x=\frac{40}{21}\)
\(\Leftrightarrow x=\frac{40}{21}:4\)
\(\Leftrightarrow x=\frac{10}{21}\)
Vậy x = \(\frac{10}{21}\)
_Chúc bạn học tốt_
NA
1
MN
24 tháng 4 2016
a) \(\frac{2}{5}+\frac{3}{5}.\left(3x-3,7\right)=\frac{-53}{10}\)
=> \(\frac{3}{5}.\left(3x-3,7\right)=\frac{-53}{10}-\frac{2}{5}\)
=> \(\frac{3}{5}.\left(3x-3,7\right)=\frac{-57}{10}\)
=> \(\left(3x-3,7\right)=\frac{-19}{5}\)
=>\(3x=\frac{-19}{5}+\frac{37}{10}\)
=>\(3x=\frac{-1}{10}\)
=>\(x=\frac{-1}{30}\)
Ko biết đúng hay sai!!?
7/9:(2+3/4x)=23/27-5/9
7/9:(2+3/4x)=8/27
2+3/4x=7/9:8/27
2+3/4x=21/8
3/4x=21/8-2
3/4x=5/8
x=5/8:3/4
x=5/6
\(\frac{7}{9}:\left(2+\frac{3}{4}x\right)+\frac{5}{9}=\frac{23}{27}\)
\(\Rightarrow\left(2+\frac{3}{4}x\right)+\frac{5}{9}=\frac{7}{9}:\frac{23}{27}=\frac{21}{23}\)
\(\Rightarrow2+\frac{3}{4}x=\frac{21}{23}-\frac{5}{9}=\frac{74}{207}\)
\(\Rightarrow\frac{3}{4}x=2-\frac{74}{207}=\frac{340}{207}\)
\(\Rightarrow x=\frac{340}{207}:\frac{3}{4}\)
\(\Rightarrow x=\frac{1360}{621}\)