\(\dfrac{x+4}{2008}+\dfrac{x+3}{2009}=\dfrac{x+2}{2010}+\dfrac{x+1}{2011}\)
\(\Leftrightarrow x+2012=0\)
hay x=-2012
\(\Rightarrow\left(\dfrac{x+4}{2008}+1\right)+\left(\dfrac{x+3}{2009}+1\right)=\left(\dfrac{x+2}{2010}+1\right)+\left(\dfrac{x+1}{2011}+1\right)\\ \Rightarrow\dfrac{x+2012}{2008}+\dfrac{x+2012}{2009}=\dfrac{x+2012}{2010}+\dfrac{x+2012}{2011}\\ \Rightarrow\left(x+2012\right)\left(\dfrac{1}{2008}+\dfrac{1}{2009}-\dfrac{1}{2010}-\dfrac{1}{2011}\right)=0\\ \Rightarrow x=-2012\)
\(\Leftrightarrow\left(\dfrac{x+4}{2008}+1\right)+\left(\dfrac{x+3}{2009}+1\right)=\left(\dfrac{x+2}{2010}+1\right)+\left(\dfrac{x+1}{2011}+1\right)\)
\(\Leftrightarrow\dfrac{x+2012}{2008}+\dfrac{x+2012}{2009}-\dfrac{x+2012}{2010}-\dfrac{x+2012}{2011}=0\)
\(\Leftrightarrow\left(x+2012\right)\left(\dfrac{1}{2008}+\dfrac{1}{2009}-\dfrac{1}{2010}-\dfrac{1}{2011}\right)=0\)
\(\Leftrightarrow x=-2012\)( do \(\dfrac{1}{2008}+\dfrac{1}{2009}-\dfrac{1}{2010}-\dfrac{1}{2011}\ne0\))
\(\dfrac{x+4}{2008}+\dfrac{x+3}{2009}=\dfrac{x+2}{2010}+\dfrac{x+1}{2011}\)
\(\left(\dfrac{x+4}{2008}+1\right)+\left(\dfrac{x+3}{2009}+1\right)-\left(\dfrac{x+2}{2010}+1\right)-\left(\dfrac{x+1}{2011}+1\right)=0\)
\(\dfrac{x+2012}{2008}+\dfrac{x+2012}{2009}-\dfrac{x+2012}{2010}-\dfrac{x+2012}{2011}=0\)
\(\left(x+2012\right)\left(\dfrac{1}{2008}+\dfrac{1}{2009}-\dfrac{1}{2010}-\dfrac{1}{2011}\right)\)
⇔\(x+2012=0\)
⇔\(x=-2012\)
\(\dfrac{x+4}{2008}+\dfrac{x+3}{2009}=\dfrac{x+2}{2010}+\dfrac{x+1}{2011}\)
<=> \(\left(\dfrac{x+4}{2008}+1\right)+\left(\dfrac{x+3}{2009}+1\right)=\left(\dfrac{x+2}{2010}+1\right)+\left(\dfrac{x+1}{2011}+1\right)\)
<=> \(\dfrac{x+2012}{2008}+\dfrac{x+2012}{2009}-\dfrac{x+2012}{2010}-\dfrac{x+2012}{2011}=0\)
<=> \(\left(x+2012\right)\left(\dfrac{1}{2008}+\dfrac{1}{2009}-\dfrac{1}{2010}-\dfrac{1}{2011}\right)=0\)
<=> \(x+2012=0\)
<=> x = -2012




