Tìm x biết:
\(x-\frac{20}{11.13}-\frac{20}{13.15}-....-\frac{20}{53.55}=\frac{3}{11}\)
\(\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+....+\frac{2}{x.\left(x+1\right)}=\frac{2}{9}\)
giúp mình với mình tick cho!
Tìm x biết:
a,\(\frac{1}{2a^2+1}:x=2\)
b,\(x-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}.........-\frac{20}{53.55}=\frac{3}{11}\)
c,\(\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+........+\frac{2}{x\left(x+1\right)}=\frac{2}{9}\)
\(2+\frac{2}{3}+\frac{2}{12}+.....+\frac{2}{X\left(X-1\right)}=1\frac{1989}{1991}\)
1989 PHẦN 1991 NHA MK VT THIẾU
\(\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+.....+\frac{2}{X\left(X+1\right)}=\frac{2}{9}\) \(X-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-.....-\frac{20}{53.55}=\frac{3}{11}\)
GIÚP MÌNH NHA MẤY BẠN 10H CHỐT NHA . AI TRẢ LỜI ĐÚNG VÀ NHANH MK TIK CHO
Bài 1: Tìm x;
x - \(\frac{20}{11.13}\) - \(\frac{20}{13.15}\) -...- \(\frac{20}{53.55}\) = \(\frac{3}{11}\)
\(\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+...+\frac{2}{x.\left(x+1\right)}=\frac{2}{9}\)
Bài 2: Tìm A biết:
A= \(\frac{7}{10}\)+\(\frac{7}{10^2}\)+ \(\frac{7}{10^3}\)+......
Bài 1:
a) \(x-\frac{20}{11.13}-\frac{20}{13.15}-...-\frac{20}{53.55}=\frac{3}{11}\)
\(x-\left(\frac{20}{11.13}+\frac{20}{13.15}+...+\frac{20}{53.55}\right)=\frac{3}{11}\)
\(x-\frac{20}{2}.\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{53}-\frac{1}{55}\right)=\frac{3}{11}\)
\(x-10.\left(\frac{1}{11}-\frac{1}{55}\right)=\frac{3}{11}\)
\(x-10\cdot\frac{4}{55}=\frac{3}{11}\)
\(x-\frac{8}{11}=\frac{3}{11}\)
\(x=1\)
b) \(\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+...+\frac{2}{x.\left(x+1\right)}=\frac{2}{9}\)
\(\frac{2}{42}+\frac{2}{56}+\frac{2}{72}+...+\frac{2}{x.\left(x+1\right)}=\frac{2}{9}\)
\(\frac{2}{6.7}+\frac{2}{7.8}+\frac{2}{8.9}+...+\frac{2}{x.\left(x+1\right)}=\frac{2}{9}\)
\(2.\left(\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2}{9}\)
\(2.\left(\frac{1}{6}-\frac{1}{x+1}\right)=\frac{2}{9}\)
\(\frac{1}{6}-\frac{1}{x+1}=\frac{1}{9}\)
\(\frac{1}{x+1}=\frac{1}{18}\)
=> x + 1 =18
x = 17
bài 2 ko bk lm, xl nha
Tìm số tự nhiên x, biết:
a, \(x-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-....-\frac{20}{53-55}=\frac{3}{11}\)
b, \(x+\frac{4}{5.9}+\frac{4}{9.13}+\frac{4}{13.17}+...+\frac{4}{41.45}=\frac{-37}{45}\)
c,\(\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+\frac{2}{x\left(x+1\right)}=\frac{2}{9}\)
Tìm x:
a) x - \(\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-...-\frac{20}{53.55}=\frac{3}{11}\)
b) \(\frac{2}{42}+\frac{2}{56}+\frac{2}{72}+...+\frac{2}{x\left(x+1\right)}=\frac{2}{9}\left(x\in N\cdot\right)\)
\(x-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-...-\frac{20}{53.55}=\frac{3}{11}\)
\(x-10\left(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{2}{53.55}\right)=\frac{3}{11}\)
\(x-10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{53}-\frac{1}{55}\right)=\frac{3}{11}\)
\(x-10.\frac{4}{55}=\frac{3}{11}\)
\(x=1\)
x-\(\left(\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{53.55}\right)=\frac{3}{11}\)
\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}+...+\frac{2}{x\left(x-1\right)}=\frac{2007}{2009}\)
a. nhân cả hai vế của đẳng thức với 1/ 10 ta có
x/10 - (2/11.13 +2/13.15+...+2/53.55)=3/11 . 1/10
x/10 - (1/11-1/13+1/13-1/15 +...+1/53-1/55) =3/110
x/10 - (1/11 - 1/55) =3/110
x/10 -4/55 = 3/110
x/10=3/110 + 4/55
x. 1/10 =1/10
x= 1/10 : 1/10 =1
b) bạn nhân cả hai vế của đẳng thức với 1/2 rồi làm tương tự
a. nhân cả hai vế của đẳng thức với \(\frac{1}{10}\). Ta có:
\(\frac{x}{10}-\left(\frac{2}{11.13}+\frac{2}{13.15}+...\frac{2}{53.55}\right)=\frac{3}{11}.\frac{1}{10}\)
\(\frac{x}{10}-\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...\frac{1}{53}-\frac{1}{55}\right)=\frac{3}{110}\)
\(\frac{x}{10}-\left(\frac{1}{11}-\frac{1}{55}\right)=\frac{3}{110}\)
\(\frac{x}{10}-\frac{-4}{55}=\frac{3}{110}\)
\(\frac{x}{10}=\frac{3}{110}+\frac{4}{55}\)
\(x.\frac{1}{10}=\frac{1}{10}\)
\(x=\frac{1}{10}:\frac{1}{10}=1\)
b. cũng thế bạn nhân hai vế của đẳng thức với \(\frac{1}{2}\) rồi làm tương tự.
Tìm x biết:
1)||x-2013|-2014|=2015
2)x-(\(\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{53.55}=\frac{3}{11}\)
(nhanh lên đc k nhỉ các bạn)
-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=\(\frac{13}{11}\)
ý b sai rồi Phạm Ngọc Thạch ak
1/2 đào đâu ra ma nhân cơ chứ
tìm số tự nhiên x biết :
x - \(\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-.......-\frac{20}{53.55}=\frac{3}{11}\)
AI NHANH MIK CHO BA TICK
Tìm x thuộc N biết:
x-\(\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-......-\frac{20}{53.55}=\frac{3}{11}\)
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