tìm x \(\in\)N \(x\)- \(\frac{20}{11.13}\)-\(\frac{20}{13.15}\)- \(\frac{20}{15.17}\)-.........- \(\frac{20}{53.55}\)=\(\frac{3}{11}\)
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
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
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
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x-\frac{20}{11\cdot13}-\frac{20}{13\cdot15}-\frac{20}{15\cdot17}-......-\frac{20}{53\cdot55}=\frac{3}{11}\)
\(\Leftrightarrow x-10\left(\frac{2}{11\cdot13}-\frac{2}{13\cdot15}-\frac{2}{15\cdot17}-.....-\frac{2}{53\cdot55}\right)=\frac{3}{11}\)
\(\Leftrightarrow x-10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+....+\frac{1}{53}-\frac{1}{55}\right)=\frac{3}{11}\)
\(\Leftrightarrow x-10\left(\frac{1}{11}-\frac{1}{55}\right)=\frac{3}{11}\)
\(\Rightarrow x=1\)
![](https://rs.olm.vn/images/avt/0.png?1311)
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
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-...-\frac{20}{53.55}=\frac{3}{11}\)
\(\Rightarrow x-\left(\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{53.55}\right)=\frac{3}{11}\)
\(\Rightarrow x-\left[10\left(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{20}{53.55}\right)\right]=\frac{3}{11}\)
\(\Rightarrow x-\left[10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{53}-\frac{1}{55}\right)\right]=\frac{3}{11}\)
\(\Rightarrow x-\left[10\left(\frac{1}{11}-\frac{1}{55}\right)\right]=\frac{3}{11}\)
\(\Rightarrow x-\left[10.\frac{4}{55}\right]=\frac{3}{11}\)
\(\Rightarrow x-\frac{8}{11}=\frac{3}{11}\)
\(\Rightarrow x=\frac{3}{11}+\frac{8}{11}\)
\(\Rightarrow x=1\)
Vậy x = 1
_Chúc bạn học tốt_
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x-\left(\frac{20}{11.13}+\frac{20}{13.15}+....+\frac{20}{53.55}\right)=\frac{3}{11}\)
\(x-10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{53}-\frac{1}{55}\right)=\frac{3}{11}\)
\(x-10\left(\frac{1}{11}-\frac{1}{55}\right)=\frac{3}{11}\)
\(x-10.\frac{4}{55}=\frac{3}{11}\)
\(x-\frac{8}{11}=\frac{3}{11}\Rightarrow x=\frac{3}{11}+\frac{8}{11}=\frac{11}{11}=1\)
\(x-\left(\frac{20}{11\cdot13}+\frac{20}{13\cdot15}+...+\frac{20}{53\cdot55}\right)=\frac{3}{11}\)
Đặt \(x-A=\frac{3}{11}\)
\(\frac{A}{10}=\frac{2}{11\cdot13}+\frac{2}{13\cdot15}+...+\frac{2}{53\cdot55}\)
\(\frac{A}{10}=\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{53}-\frac{1}{55}\)
\(\frac{A}{10}=\frac{1}{11}-\frac{1}{55}\)
\(\frac{A}{10}=\frac{4}{55}\)
\(A=\frac{8}{11}\)
\(\Rightarrow x-\frac{8}{11}=\frac{3}{11}\)
\(\Rightarrow x=\frac{3}{11}+\frac{8}{11}\)
\(\Rightarrow x=1\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-...-\frac{20}{53.55}=\frac{3}{11}\)
\(x-10\left(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{2}{53.55}\right)=\frac{3}{11}\)
\(x-10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{53}-\frac{1}{55}\right)=\frac{3}{11}\)
\(x-10.\frac{4}{55}=\frac{3}{11}\)
\(x=1\)
![](https://rs.olm.vn/images/avt/0.png?1311)
-Nếu |x-2013|-2014=2015->|x-2013| = 4029
+ Nếu x-2013 =4029 -> x= 6042
+ Nếu x-2013 = -4029 -> x = -2016
- Nếu |x-2013|-2014= -2015 -> |x-2013| = -1 (loại vì |x-2013| \(\ge\)0 )
Vậy x= 6042 ; x=-2016 là các giá trị cần tìm.
\(x-\left(\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{53.55}\right)=\frac{3}{11}\)
=> \(x-\left(20\times\frac{1}{11.13}+20\times\frac{1}{13.15}+20\times\frac{1}{15.17}+...+20\times\frac{1}{53.55}\right)=\frac{3}{11}\)
\(x-20\times\left(\frac{1}{11.13}+\frac{1}{13.15}+\frac{1}{15.17}+...+\frac{1}{53.55}\right)=\frac{3}{11}\)
\(x-20\times\left(\frac{1}{2}\times\left(\frac{1}{11}-\frac{1}{13}\right)+\frac{1}{2}\times\left(\frac{1}{13}-\frac{1}{15}\right)+\frac{1}{2}\times\times+...+\frac{1}{2}\times\left(\frac{1}{53}-\frac{1}{55}\right)\right)=\frac{3}{11}\)
\(x-20\times\frac{1}{2}\times\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-...-\frac{1}{53}+\frac{1}{53}-\frac{1}{55}\right)=\frac{3}{11}\)
\(x-10\times\left(\frac{1}{11}-\frac{1}{55}\right)=\frac{3}{11}\)
\(x-10\times\frac{4}{55}=\frac{3}{11}\)
\(x-\frac{10}{11}=\frac{3}{11}\)
=> \(x=\frac{3}{11}+\frac{10}{11}=\frac{13}{11}\)
Vậy x=\(\frac{13}{11}\)
\(x-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-.....-\frac{20}{53.55}=\frac{3}{11}\)
\(x-\left(\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+....+\frac{20}{53.55}\right)=\frac{3}{11}\)
\(x-10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+.....+\frac{1}{53}-\frac{1}{55}\right)=\frac{3}{11}\)
\(x-10\left(\frac{1}{11}-\frac{1}{55}\right)=\frac{3}{11}\)
\(x-\frac{40}{55}=\frac{3}{11}\)
\(x=\frac{3}{11}+\frac{40}{55}\)
\(x=1\)