VÌ \(\left|x\right|\ge0;\left|y\right|\ge0;\left|z\right|\ge0\)NÊN ĐỂ\(\left|x\right|+\left|y\right|+\left|z\right|=0\)\(\Leftrightarrow\hept{\begin{cases}\left|x\right|=0\\\left|y\right|=0\\\left|z\right|=0\end{cases}\Leftrightarrow\hept{\begin{cases}x=0\\y=0\\z=0\end{cases}}}\)