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2011 + 2010 + 2009 + ... + x = 2011
<=> 2011+ 2010 + 2009 +......+ 0 + (-1) + (-2) + (-3)+.......+ x -2011 = 0
<=> x = -2010
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b) x - 17 = ( - 11 ) . ( - 5 )
x -17 = 55
x = 55 + 17
x = 72
Vậy x =...
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Ta có 2008/2009 < 1; 2009/2010 < 1; 2010/2011 < 1; 2011/2012 < 1
Nên : 2008/2009 + 2009/2010 + 2010/2011 + 2011/2012 < 1 + 1 + 1 + 1
Ta có 2008/2009 < 1; 2009/2010 < 1; 2010/2011 < 1; 2011/2012 < 1
Nên : 2008/2009 + 2009/2010 + 2010/2011 + 2011/2012 < 1 + 1 + 1 + 1
Hay A < 4
A < B
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X x 2011-X=2011x2009+2011
Xx(2011-1)=2011x(2009+1)
Xx2010 = 2011x2010
=> X=2011
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\(\frac{x-28-124}{2011}+\frac{x-124-2011}{28}+\frac{x-2011-28}{124}=3\)
<=> \(\left(\frac{x-152}{2011}-1\right)+\left(\frac{x-2135}{28}-1\right)+\left(\frac{x-2039}{124}-1\right)=0\)
<=> \(\frac{x-2163}{2011}+\frac{x-2163}{28}+\frac{x-2163}{124}=0\)
<=> \(\left(x-2163\right)\left(\frac{1}{2011}+\frac{1}{28}+\frac{1}{124}\right)=0\)
<=> \(x-2163=0\)(vì \(\frac{1}{2011}+\frac{1}{28}+\frac{1}{124}\ne0\)
<=> \(x=2163\)
\(\frac{x-28-124}{2011}+\frac{x-124-2011}{28}+\frac{x-2011-28}{124}=3\)
<=> \(\frac{x-28-124}{2011}+\frac{x-124-2011}{28}+\frac{x-2011-28}{124}-3=0\)
<=> \(\left(\frac{x-28-124}{2011}-1\right)+\left(\frac{x-124-2011}{28}-1\right)+\left(\frac{x-2011-28}{124}-1\right)=0\)
<=> \(\frac{x-28-124-2011}{2011}+\frac{x-124-2011-28}{28}+\frac{x-2011-28-124}{124}=0\)
<=> \(\frac{x-2163}{2011}+\frac{x-2163}{28}+\frac{x-2163}{124}=0\)
<=> \(\left(x-2163\right)\left(\frac{1}{2011}+\frac{1}{28}+\frac{1}{124}\right)=0\)
Vì \(\frac{1}{2011}+\frac{1}{28}+\frac{1}{124}\ne0\)
=> \(x-2163=0\)
=> \(x=2163\)
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x . 2011 - x = 2011 . 2009 - 2011
x.(2011 - 1) = 4038088
x . 2010 = 4038088
x = 4038088: 2010
x = 2008,999005
X x 2011-X = 2011 x 2009 - 2011
X x ( 2011-1) = 2011 x (2009- 1)
X x 2010 = 2011 x 2010
=> X=2011
X x 2011 - X x 1 = 2011 x 2 +2009
X x ( 2011 - 1 ) = 4022 + 2009
X x 2010 = 6031
2010
X x 2011 - X = 2011 + 2009 + 2011
X x ( 2011 - 1 ) = 2011 x ( 2009 + 1 )
X x 2010 = 2011 x 2010
X = 2011