Giải:
Đặt \(A=\left|x\right|+\left|x-1\right|+\left|x-2\right|\)
Vì \(\Leftrightarrow\left\{{}\begin{matrix}\left|x\right|\ge x\\\left|x-1\right|\ge x-1\\\left|x-2\right|\ge x-2\end{matrix}\right.\)
Nên \(\left|x\right|+\left|x-1\right|+\left|x-2\right|\ge x+x-1+x-2\)
\(\Leftrightarrow\left|x\right|+\left|x-1\right|+\left|x-2\right|\ge3x-3\)
Hay \(A\ge3x-3\)
Vậy ...