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18 tháng 7 2017

\(3.\)

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

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

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

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

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

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

13 tháng 3 2016

a.N=1-5-9+13+17-21+...+2001-2005-2009+2013+2017

N = ( 1 - 5 - 9 + 13 ) + ( 17 - 21 - 25 + 29 ) + .... + ( 2001 - 2005 - 2009 + 2013 ) + 2017

N = 0 + 0 + ... + 0 + 2017

N = 2017

29 tháng 8 2017

cậu có thể làm dễ hiểu được  ko

27 tháng 1 2019

1.

ta có: 2009A= (2009^2010+ 2009)/ (2009^2010+1)= (2009^10+1+2008)/(2009^2010+1)=1+ [2008/(2009^2010+1)]

làm tương tự như trên ta được :

2009B=1-[4016/(2009^2011-2)]

lại có:

2009A= .............(nt) > 1

2009B=...........<1

=>2009A>2009B

=>A>B

27 tháng 1 2019

câu 2 và 3 thì làm sao bạn

19 tháng 7 2016

a)\(\frac{2}{6}+\frac{2}{12}+...+\frac{2}{x\left(x+1\right)}=\frac{2}{2013}\)

\(\frac{2}{2.3}+\frac{2}{3.4}+...+\frac{2}{x\left(x+1\right)}=\frac{2}{2013}\)

\(2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2}{2013}\)

\(\frac{1}{2}-\frac{1}{x+1}=\frac{1}{2013}\)

đề sai

b)\(\frac{x+4}{2000}+1+\frac{x+3}{2001}+1=\frac{x+2}{2002}+1+\frac{x+1}{2003}+1\)

\(\frac{x+2004}{2000}+\frac{x+2004}{2001}=\frac{x+2004}{2002}+\frac{x+2004}{2003}\)

\(\frac{x+2004}{2000}+\frac{x+2004}{2001}-\frac{x+2004}{2002}-\frac{x+2004}{2003}=0\)

\(\left(x+2004\right)\left(\frac{1}{2000}+\frac{1}{2001}-\frac{1}{2002}-\frac{1}{2003}\right)=0\)

\(x+2004=0\).Do \(\frac{1}{2000}+\frac{1}{2001}-\frac{1}{2002}-\frac{1}{2003}\ne0\)

\(x=-2004\)

c)\(\frac{x+5}{205}-1+\frac{x+4}{204}-1+\frac{x+3}{203}-1=\frac{x+166}{366}-1+\frac{x+167}{367}-1+\frac{x+168}{368}-1\)

\(\frac{x-200}{205}+\frac{x-200}{204}+\frac{x-200}{203}=\frac{x-200}{366}+\frac{x-200}{367}+\frac{x-200}{368}\)

\(\frac{x-200}{205}+\frac{x-200}{204}+\frac{x-200}{203}-\frac{x-200}{366}-\frac{x-200}{367}-\frac{x-200}{368}=0\)

\(\left(x-200\right)\left(\frac{1}{205}+\frac{1}{204}+\frac{1}{203}-\frac{1}{366}-\frac{1}{367}-\frac{1}{368}\right)=0\)

\(x-200=0\).Do\(\frac{1}{205}+\frac{1}{204}+\frac{1}{203}-\frac{1}{366}-\frac{1}{367}-\frac{1}{368}\ne0\)

\(x=200\)

d)chịu

19 tháng 12 2016

de thieu

1 tháng 1 2017

x=-2004

11 tháng 7 2015

\(\frac{x+2}{2012}+\frac{x+3}{2011}=\frac{x+4}{2010}+\frac{x+5}{2009}\)

\(\Rightarrow\frac{x+2}{2012}+1+\frac{x+3}{2011}+1=\frac{x+4}{2010}+1+\frac{x+5}{2009}+1\)

\(\frac{x+2}{2012}+\frac{2012}{2012}+\frac{x+3}{2011}+\frac{2011}{2011}=\frac{x+4}{2010}+\frac{2010}{2010}+\frac{x+5}{2009}+\frac{2009}{2009}\)

\(\frac{x+2014}{2012}+\frac{x+2014}{2011}=\frac{x+2014}{2010}+\frac{x+2014}{2009}\)

\(\frac{x+2014}{2012}+\frac{x+2014}{2011}-\frac{x+2014}{2010}-\frac{x+2014}{2009}=0\)

\(\left(x+2014\right)\left(\frac{1}{2012}+\frac{1}{2011}-\frac{1}{2010}-\frac{1}{2009}\right)=0\)

mà \(\frac{1}{2012}+\frac{1}{2011}-\frac{1}{2010}-\frac{1}{2009}\ne0\)

nên \(x+2014=0\)

      \(x=-2014\)

16 tháng 1 2019

A=2.998508205

B=0.999502735

suy ra A>B

30 tháng 5 2019

                                              Bài giải

Theo bài ra :  

\(A=\frac{2009}{2010}+\frac{2010}{2011}+\frac{2011}{2012}\)

\(B=\frac{2009+2010+2011}{2010+2011+2012}=\frac{2009}{2010+2011+2012}+\frac{2010}{2010+2011+2012}+\frac{2011}{2010+2011+2012}\)

Ta có : 

\(\frac{2009}{2010}>\frac{2009}{2010+2011+2012}\)

\(\frac{2010}{2011}>\frac{2010}{2010+2011+2012}\)

\(\frac{2011}{2012}>\frac{2011}{2010+2011+2012}\)

\(\Rightarrow\text{ }\frac{2009}{2010}+\frac{2010}{2011}+\frac{2011}{2012}>\frac{2009}{2010+2011+2012}+\frac{2010}{2010+2011+2012}+\frac{2011}{2010+2011+2012}\)

\(\Rightarrow\text{ }A>B\)

28 tháng 7 2015

\(2011+2010+2009+...+x=2011\)

\(2011+\left(2010+2009+...+x\right)=2011\)

\(2010+2009+...+x=2011-2011\)

\(2010+2009+...+x=0\)

\(\rightarrow\) Từ 2010->x có: x số

\(\rightarrow\) \(\frac{\left(x+2010\right).x}{2}=0\)

       \(\left(x+2010\right).x=0.2\)

       \(\left(x+2010\right).x=0\)

\(\Rightarrow x+2010=0\)

       \(x=0+2010\)

       \(x=-2010\)

\(V\text{ậy}\) \(x=-2010\)

Tâm Trần Hiếu sai rùi vì 0-2010 mới bằng -2010

mik fan Phong ca nè bạn