Đáp án:
\(\overrightarrow a = \left( {5;\,\, - 15} \right)\)
Giải thích các bước giải:
\(\begin{array}{l}
A\left( {1;\,\,2} \right),\,\,\,B\left( {6;\,\,2} \right),\,\,\,C\left( {4;\,\,5} \right)\\
\Rightarrow \left\{ \begin{array}{l}
\overrightarrow {AB} = \left( {5;\,\,0} \right)\\
\overrightarrow {BC} = \left( { - 2;\,\,3} \right)\\
\overrightarrow {CA} = \left( { - 3; - 3} \right)
\end{array} \right.\\
\Rightarrow \overrightarrow a = \overrightarrow {AB} - 3\overrightarrow {BC} + 2\overrightarrow {CA} \\
= \left( {5;\,\,0} \right) - 3\left( { - 2;\,\,3} \right) + 2\left( { - 3; - 3} \right)\\
= \left( {5 + 3.2 + 2.\left( { - 3} \right);\,\, - 3.3 + 2\left( { - 3} \right)} \right)\\
= \left( {5;\,\, - 15} \right).
\end{array}\)
