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11 tháng 1 2020

\(x-\frac{20}{11\cdot13}-\frac{20}{13\cdot15}-\frac{20}{15\cdot17}-......-\frac{20}{53\cdot55}=\frac{3}{11}\)

\(\Leftrightarrow x-10\left(\frac{2}{11\cdot13}-\frac{2}{13\cdot15}-\frac{2}{15\cdot17}-.....-\frac{2}{53\cdot55}\right)=\frac{3}{11}\)

\(\Leftrightarrow x-10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+....+\frac{1}{53}-\frac{1}{55}\right)=\frac{3}{11}\)

\(\Leftrightarrow x-10\left(\frac{1}{11}-\frac{1}{55}\right)=\frac{3}{11}\)

\(\Rightarrow x=1\)

29 tháng 7 2018

\(x-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-...-\frac{20}{53.55}=\frac{3}{11}\)

\(\Rightarrow x-\left(\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{53.55}\right)=\frac{3}{11}\)

\(\Rightarrow x-\left[10\left(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{20}{53.55}\right)\right]=\frac{3}{11}\)

\(\Rightarrow x-\left[10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{53}-\frac{1}{55}\right)\right]=\frac{3}{11}\)

\(\Rightarrow x-\left[10\left(\frac{1}{11}-\frac{1}{55}\right)\right]=\frac{3}{11}\)

\(\Rightarrow x-\left[10.\frac{4}{55}\right]=\frac{3}{11}\)

\(\Rightarrow x-\frac{8}{11}=\frac{3}{11}\)

\(\Rightarrow x=\frac{3}{11}+\frac{8}{11}\)

\(\Rightarrow x=1\)

Vậy x = 1

_Chúc bạn học tốt_

18 tháng 8 2018

\(x-\left(\frac{20}{11.13}+\frac{20}{13.15}+....+\frac{20}{53.55}\right)=\frac{3}{11}\)

\(x-10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{53}-\frac{1}{55}\right)=\frac{3}{11}\)

\(x-10\left(\frac{1}{11}-\frac{1}{55}\right)=\frac{3}{11}\)

\(x-10.\frac{4}{55}=\frac{3}{11}\)

\(x-\frac{8}{11}=\frac{3}{11}\Rightarrow x=\frac{3}{11}+\frac{8}{11}=\frac{11}{11}=1\)

18 tháng 8 2018

\(x-\left(\frac{20}{11\cdot13}+\frac{20}{13\cdot15}+...+\frac{20}{53\cdot55}\right)=\frac{3}{11}\)

Đặt \(x-A=\frac{3}{11}\)

\(\frac{A}{10}=\frac{2}{11\cdot13}+\frac{2}{13\cdot15}+...+\frac{2}{53\cdot55}\)

\(\frac{A}{10}=\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{53}-\frac{1}{55}\)

\(\frac{A}{10}=\frac{1}{11}-\frac{1}{55}\)

\(\frac{A}{10}=\frac{4}{55}\)

\(A=\frac{8}{11}\)

\(\Rightarrow x-\frac{8}{11}=\frac{3}{11}\)

\(\Rightarrow x=\frac{3}{11}+\frac{8}{11}\)

\(\Rightarrow x=1\)

21 tháng 2 2016

x-20/11.13-20/13.15-...-20/53.55=3/11

=>x-(20/11.13+20/13.15+...+20/53.55)=3/11

Rồi tính tổng trong ngoặc là OK

21 tháng 2 2016

ta có: x-\(\left(\frac{20}{11.13}-\frac{20}{13.15}-...-\frac{20}{53.55}\right)=\frac{3}{11}\)

 \(x-\left[20\left(\frac{1}{11.13}-\frac{1}{13.15}-...-\frac{1}{53.55}\right)\right]=\frac{3}{11}\)

\(x-\left[20\left(\frac{2}{11.13}-\frac{2}{13.15}-...-\frac{2}{53.55}\right)\right]=\frac{3}{11}\)

\(x-\left[20\left(\frac{1}{11}+\frac{1}{13}-\frac{1}{13}+...-\frac{1}{53}+\frac{1}{55}\right)\right]=\frac{3}{11}\)

\(x-\left[20\left(\frac{1}{11}+\frac{1}{55}\right)\right]=\frac{3}{11}\)

\(x-\left(\frac{20.6}{55}\right)=\frac{3}{11}\)

\(x-\frac{24}{11}=\frac{3}{11}\)

\(x=\frac{3}{11}+\frac{24}{11}\)

\(x=\frac{27}{11}\)

1 tháng 4 2017

x-10( 2/11.13+2/13.15+...+2/53.55)=3/11

x-10(1/11-1/55)=3/11

x-10.4/55=3/11

x-40/55=3/11

x=3/11+40/55

x= 1

10 tháng 4 2018

x-10.(2/11.13+2/13.15+....+2/53.55)=3/11

x-10.(1/11-1/13+...+1/53-1/55)=3/11

x-10.(1/11-1/55)=3/11

x-10.4/55=3/11

x-8/11=3/11

x=1

Nhớ k cho mình nhé

21 tháng 3 2016

Hình như sai đề rùi bạn ạ

21 tháng 3 2016

2x=1/11-1/13.........................-1/53-1/55+3/11

2x=1/11-1/55+3/11

2x=19/55

x=19/55 chia 2

x=19/110 

8 tháng 8 2015

x - \(10\left(\frac{2}{11.13}+\frac{2}{13.15}+..+\frac{2}{53.55}\right)=22\)

\(x-10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+..+\frac{1}{53}-\frac{1}{55}\right)=22\)

\(x-10\left(\frac{1}{11}-\frac{1}{55}\right)=22\)

\(x-10\cdot\frac{4}{55}=22\)

\(x-\frac{40}{55}=22\)

\(x=22+\frac{40}{55}=\frac{250}{11}\)