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X x 2011 - X x 1 = 2011 x 2 +2009
X x ( 2011 - 1 ) = 4022 + 2009
X x 2010 = 6031
- X = 6031
2010
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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
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x * 2011 - x = 2011 * 2009 + 2011
x*(2011-1) = 2011*(2009 +1 )
x * 2010 = 2011 * 2010
x= 2011
\(x.2011-x=2011.2009+2011\)
\(\Leftrightarrow2010x=4042100\)
\(\Leftrightarrow x=4042100:2010\)
\(\Leftrightarrow x=\dfrac{4042100}{2010}\)
Vậy ...
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1.1/3+1/6+1/10+...+2/x.(x+1)=2007/2009
=>2/6+2/12+2/20+...+2/x.(x+1)=2007/2009
=>1/2-1/3+1/3-1/4+1/4-1/5+...+1/x-1/(x+1)=2007/2009:2
=>1/2-1/(x+1)=2007/4018
=>1/(x+1)=1/2-2007/4018
=>1/x+1=1/2009
=>x+1=2009
=>x=2009-2008
=>x=1
vậy x=1
X x 2011-X=2011x2009+2011
Xx(2011-1)=2011x(2009+1)
Xx2010 = 2011x2010
=> X=2011
x=2011