d: =>x+1/2=0 hoặc 2/3-2x=0
=>x=-1/2 hoặc x=1/3
b: \(\Leftrightarrow1-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{11}+...+\dfrac{1}{5x+1}-\dfrac{1}{5x+6}=\dfrac{2010}{2011}\)
\(\Leftrightarrow1-\dfrac{1}{5x+6}=\dfrac{2010}{2011}\)
=>1/(5x+6)=1/2011
=>5x+6=2011
=>5x=2005
hay x=401
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