11.13+13.15+15.17+............+31.33
K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Những câu hỏi liên quan
18 tháng 3 2018
Gọi A = 2/11.13 +2/13.15+2/15.17 +...+2/53.55
=> A = 1/11-1/13+1/13-1/15+...+1/53-1/55
=> A = 1/11-1/55
=> A = 4/55
Đúng 100%
2
4
30 tháng 5 2019
\(\frac{2}{11.13}+\frac{2}{13.15}+.....+\frac{2}{209.211}\)
\(=\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}\)\(+.....+\frac{1}{209}-\frac{1}{211}\)
\(=\frac{1}{11}-\frac{1}{211}=\frac{200}{2321}\)
hok tốt
S
30 tháng 5 2019
Đặt \(A=\text{2 : [ 11.13 ] + 2 : [ 13.15 ] + 2 : [ 15.17 ] + ...+ 2 : [ 209.211]}\)
\(\Rightarrow A=\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}...+\frac{2}{209.211}\)
\(\Rightarrow A=\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{209}-\frac{1}{211}\)
\(\Rightarrow A=\frac{1}{11}-\frac{1}{211}\)
\(\Rightarrow A=\frac{200}{2321}\)
~Study well~
Sai thì thôi nhé :D !
LK
21 tháng 1 2022
eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
NH
5 tháng 7 2016
\(C=\frac{1}{11.13}+\frac{1}{13.15}+\frac{1}{15.17}+...+\frac{1}{2015.2017}\)
\(2C=\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{2}{2015.2017}\)
\(2C=\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{2015}-\frac{1}{2017}\)
\(2C=\frac{1}{11}-\frac{1}{2017}\)
\(2C=\frac{2006}{22187}\)
\(C=\frac{1003}{22187}\)
5 tháng 7 2016
C = 1/11 . 13 + 1/13 . 15 + 1/15 . 17 + ........ + 1/2015 . 2017
C = 1/11 - 1/13 + 1/13 - 1/15 + 1/15 - 1/17 + ......... + 1/2015 - 1/2017
C = 1/11 - 1/2017
C = 2006/22187
NP
2
N
20 tháng 7 2015
Đặt \(A=\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+\frac{2}{17.19}+\frac{2}{19.21}^{ }\)
\(A=\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+\frac{1}{17}-\frac{1}{19}+\frac{1}{19}-\frac{1}{21}\)
\(A=\frac{1}{11}-\frac{1}{21}\)
\(A=\frac{10}{231}\)
Thay \(A=\frac{10}{231}\) vào ta có
\(\frac{10}{231}.462-x=19\)
\(20-x=19\)
\(x=20-19\)
\(x=1\)
ND
1
27 tháng 2 2016
=(1/11-1/13)+(1/13-1/15)+(1/15-1/17)+(1/17-1/19)+(1/19-1/21)*462-X=19
=(1/11-1/21)*462-X=19
=10/231*462-X=19
=20-X=19
=X=20-19
=X=1
lop nam cung lam duoc
DQ
2
2 tháng 3 2019
\(x-\dfrac{20}{11.13}-\dfrac{20}{23.15}-....-\dfrac{20}{53.55}=\dfrac{3}{11}\)
\(x-\left(\dfrac{20}{11.13}+\dfrac{20}{13.15}+....+\dfrac{20}{53.55}\right)=\dfrac{3}{11}\)
\(x-10\left(\dfrac{1}{11}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{15}+...+\dfrac{1}{53}-\dfrac{1}{55}\right)=\dfrac{3}{11}\)
\(x-10\left(\dfrac{1}{11}-\dfrac{1}{55}\right)=\dfrac{3}{11}\)
\(x-\dfrac{8}{11}=\dfrac{3}{11}\)
=> \(x=\dfrac{3}{11}+\dfrac{8}{11}=1\)
TN
20 tháng 5 2019
Ta có:
x-\(\frac{20}{11.13}\)-\(\frac{20}{13.15}\)-\(\frac{20}{15.17}\)-...-\(\frac{20}{53.57}\)=\(\frac{3}{11}\)
\(\Rightarrow\)\(\frac{20}{11.13}\)-\(\frac{20}{13.15}\)-\(\frac{20}{15.17}\)-...-\(\frac{20}{53.57}\)= x-\(\frac{3}{11}\)
\(\frac{1}{10}\).\((\frac{20}{11.13}.\frac{20}{13.15}.\frac{20}{15.17}...\frac{20}{53.57})\)= x-\(\frac{3}{11}\)
\(\frac{2}{11.13}\).\(\frac{2}{13.15}\).\(\frac{2}{15.17}\)...\(\frac{2}{53.57}\)= x-\(\frac{3}{11}\)
\(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}\)-\(\frac{1}{17}\)+...+\(\frac{1}{53}\)-\(\frac{1}{57}\)=x-\(\frac{3}{11}\)
\(\frac{1}{11}-\frac{1}{57}\)=x-\(\frac{3}{11}\)
\(\frac{46}{627}\)=x-\(\frac{3}{11}\)
x=\(\frac{46}{627}\)-\(\frac{3}{11}\)
Vậy x=\(\frac{-125}{627}\)
= 33.(11+13+15+....+31)
=33.231
= 7623
thanks