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4 tháng 2 2019

\(\frac{2}{2.3}+\frac{2}{3.4}+\frac{2}{4.5}+...+\frac{2}{x.\left(x+1\right)}=\frac{2008}{2010}.\)

\(2.\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2008}{2010}\)

\(\frac{1}{2}-\frac{1}{x+1}=\frac{502}{1005}\)

\(\frac{1}{x+1}=\frac{1}{2010}\)

=> x + 1 = 2010

=> x = 2009

4 tháng 2 2019

Ta có : \(\frac{2}{2\times3}+\frac{2}{3\times4}+....+\frac{2}{x\times\left(x+1\right)}=\frac{2008}{2010}\)

\(\Rightarrow2\times\left(\frac{1}{2\times3}+.....+\frac{1}{x\times\left(x+1\right)}\right)=\frac{1004}{1005}\)

\(\Rightarrow2\times\left(\frac{1}{2}-\frac{1}{3}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{1004}{1005}\)

\(\Rightarrow\frac{1}{2}-\frac{1}{x+1}=\frac{1004}{1005}:2\)

\(\Rightarrow\frac{1}{2}-\frac{1}{x+1}=\frac{502}{1005}\)

\(\Rightarrow\frac{1}{x+1}=\frac{1}{2}-\frac{502}{1005}=\frac{1}{2010}\)

\(\Rightarrow x+1=2010\)

\(\Rightarrow x=2010-1=2009\)

18 tháng 7 2017

\(3.\)

\(\frac{x-1}{2011}+\frac{x-2}{2010}+\frac{x-3}{2009}=\frac{x-4}{2008}\)

\(\Rightarrow\)\(\frac{x-1}{2011}-1+\frac{x-2}{2010}-1+\frac{x-3}{2009}-1-\frac{x-4}{2008}+1+2=0\)

\(\Rightarrow\)\(\frac{x-1}{2011}-\frac{2011}{2011}+\frac{x-2}{2010}-\frac{2010}{2010}+\frac{x-3}{2009}-\frac{2009}{2009}-\frac{x-4}{2008}+\frac{2008}{2008}=0\)

\(\Rightarrow\)\(\frac{x-2012}{2011}+\frac{x-2012}{2010}+\frac{x-2012}{2009}-\frac{x-2012}{2008}=0\)

\(\Rightarrow\)\(x-2012\left(\frac{1}{2011}+\frac{1}{2010}+\frac{1}{2009}+\frac{1}{2008}\right)=0\)

\(\Rightarrow\)\(x=2012\)

24 tháng 7 2017

\(\dfrac{x+1}{2011}+\dfrac{x+2}{2010}+\dfrac{x+3}{2009}+\dfrac{x+4}{2008}=-4\)

\(\Rightarrow\dfrac{x+1}{2011}+1+\dfrac{x+2}{2010}+1+\dfrac{x+3}{2009}+1+\dfrac{x+4}{2008}+1=0\)

\(\Rightarrow\dfrac{x+2012}{2011}+\dfrac{x+2012}{2010}+\dfrac{x+2012}{2009}+\dfrac{x+2012}{2008}=0\)

\(\Rightarrow\left(x+2012\right)\left(\dfrac{1}{2011}+\dfrac{1}{2010}+\dfrac{1}{2009}+\dfrac{1}{2008}\right)=0\)

\(\dfrac{1}{2011}+\dfrac{1}{2010}+\dfrac{1}{2009}+\dfrac{1}{2008}\ne0\)

\(\Rightarrow x+2012=0\Rightarrow x=-2012\)

Vậy x = -2012

24 tháng 7 2017

\(\dfrac{x+1}{2011}+\dfrac{x+2}{2010}+\dfrac{x+3}{2009}+\dfrac{x+4}{2008}=-4\\ \Leftrightarrow1+\dfrac{x+1}{2011}+1+\dfrac{x+2}{2010}+1+\dfrac{x+3}{2009}+1+\dfrac{x+4}{2008}=0\\ \Leftrightarrow\dfrac{x+2012}{2011}+\dfrac{x+2012}{2010}+\dfrac{x+2012}{2009}+\dfrac{x+2012}{2008}=0\\ \Leftrightarrow \left(x+2012\right)\left(\dfrac{1}{2011}+\dfrac{1}{2010}+\dfrac{1}{2009}+\dfrac{1}{2008}\right)=0\\ \Rightarrow x+2012=0\left(\dfrac{1}{2011}+\dfrac{1}{2010}+\dfrac{1}{2009}+\dfrac{1}{2008}>0\right)\\ \Rightarrow x=-2012\)

Vậy \(x=-2012\)

29 tháng 4 2018

Đề bài yêu cầu gì zậy?

10 tháng 7 2016

(2008 x 2009 x 2010 x 2011) x (1 + 1/2 : 3/2 - 4/3)

=(2008 x 2009 x 2010 x 2011) x (1 + 1/3 - 4/3)

=(2008 x 2009 x 2010 x 2011) x (4/3 - 4/3)

=(2008 x 2009 x 2010 x 2011) x 0

=0

10 tháng 7 2016

đáp số:0

ủng hộ nha

20 tháng 11 2017

a)   

  200 - ( 2 . x + 6 ) = 8 . 2 

  200 - ( 2 . x + 6 ) = 16

             2 . x + 6    = 200 - 16

             2 . x + 6    =   184 

                  x + 6    =  184 : 2

                 x + 6     =   92 

                 x           = 92 - 6 

                  x          =   86

b)

2 . x : 4 = 16 

    x : 4  =  16 : 2

    x : 4  =     8

    x       =   8 . 4  

    x       =    32

c)

  2008 . x : 2008 . 5 = 2008 . 3

  2008. ( x : 5 )         =  6024

              x : 5           =   6024 : 2008     

              x : 5           =      3

             x                 = 3 . 5 

             x                 = 15 

7 tháng 4 2022

`Answer:`

`1/3+1/6+1/10+...+2/(x.(x+1))=2008/2010`

`=2/6+2/12+2/20+...+2/(x.(x+1))=2008/2010`

`=2/(2.3)+2/(3.4)+2/(4.5)+...+(2)/(x.(x+1))=2008/2010`

`=2.(1/2-1/3+1/3-1/4+...+1/x(x+1))=2008/2010`

`=1/2-1/3+1/3-1/4+...+1/x-1/(x+1)=1004/2010`

`=1/2-1/(x+1)=1004/2010`

`=>1/(x+1)=1/2-1004/2010`

`=>1/(x+1)=1/2010`

`=>x+1=2010`

`=>x=2010-1`

`=>x=2009`