\(\begin{array}{l}
M_o(1;2;3),\quad M_1(1+t;2+t;3+t),\quad M_2(1+2t; 2+2t; 3+2t)\\
\Rightarrow \begin{cases}
\overrightarrow{M_oM_1}=(t;t;t)\\
\overrightarrow{M_oM_2}=(2t;2t;2t)
\end{cases}\\
\Rightarrow \overrightarrow{M_oM_2}=2\overrightarrow{M_oM_1}\\
\Rightarrow \overrightarrow{M_oM_2}\ \text{và}\ \overrightarrow{M_oM_1}\ \text{cùng phương}\\
\Rightarrow M_o,\ M_1,\ M_2\ \text{thẳng hàng}
\end{array}\)