Giải phương trình (3-x)/2009-(2-x)/2010+(1-x)/2011=-1

* Hướng dẫn giải

$\begin{array}{l}\frac{3-x}{2009}-\frac{2-x}{2010}+\frac{1-x}{2011}=-1\iff \frac{3-x}{2009}+1-\frac{2-x}{2010}-1+\frac{1-x}{2011}+1=0\\ \iff \left(2012-x\right)\left(\frac{1}{2009}-\frac{1}{2010}+\frac{1}{2011}\right)=0\iff x=2012\end{array}$