có 1/x(x+1)= 1/x + 1/2011
=> 1/x - 1/x+1=1/x+ 1/2011
=> -1/x+1=1/x-1/x+1/2011
=>-1/x+1=1/2011
=> -(x+1)=2011
=> x+1 = -2011
=>x=-2011-1=-2012
vậy x= -2012
\(\frac{1}{x\left(x+1\right)}=\frac{1}{x}+\frac{1}{2011}\)
\(\frac{1}{x\left(x+1\right)}-\frac{1}{x}=2011\)
\(\frac{1-x+1}{x\left(x+1\right)}=\frac{1}{2011}\)
\(\frac{x}{x\left(x+1\right)}=\frac{1}{2011}\)
x(x+1)=2011x
=>x+1=2011
=>x=2010