Tìm x,y,z thuộc Q biết:|x-2/3|+|x+y+3/4|+|y-z-5/6|=0

$\left|x-\frac{2}{3}\right|+\left|x+y+\frac{3}{4}\right|+\left|y-z-\frac{5}{6}\right|=0$ mà $\left|x-\frac{2}{3}\right|\ge 0;\left|x+y+\frac{3}{4}\right|\ge 0;\left|y-z-\frac{5}{6}\right|\ge 0$

$\Rightarrow \left\{\begin{array}{l}\left|x-\frac{2}{3}\right|=0\\ \left|x+y+\frac{3}{4}\right|=0\\ \left|y-z-\frac{5}{6}\right|=0\end{array}\right.\Rightarrow \left\{\begin{array}{l}x=\frac{2}{3}\\ y=-\frac{3}{4}-x\\ z=y-\frac{5}{6}\end{array}\right.\Rightarrow \left\{\begin{array}{l}x=\frac{2}{3}\\ y=-\frac{17}{12}\\ z=-\frac{9}{4}\end{array}\right.$ 

Vậy $x=\frac{2}{3}$; $y=-\frac{17}{12}$; $z=-\frac{9}{4}$