\(\begin{array}{l}
14)\,\,\overrightarrow {OA} + 2\overrightarrow {OB} - 3\overrightarrow {OC} = \overrightarrow 0 \\
\Leftrightarrow \overrightarrow {OA} - \overrightarrow {OC} + 2\overrightarrow {OB} - 2\overrightarrow {OC} = \overrightarrow 0 \\
\Leftrightarrow \overrightarrow {CA} = 2\overrightarrow {BC} \\
\Rightarrow \overline {A,B,C}
\end{array}\)
15) Em tự vẽ hình nhé
\(\begin{array}{l}
\overrightarrow {AH} = \overrightarrow {AB} + \overrightarrow {BH} = \overrightarrow {AB} + \dfrac{1}{5}\overrightarrow {BC} \\
\overrightarrow {KH} = \overrightarrow {KB} + \overrightarrow {BH} = - \dfrac{1}{6}\overrightarrow {BD} + \dfrac{1}{5}\overrightarrow {BC} \\
= - \dfrac{1}{6}\left( {\overrightarrow {BA} + \overrightarrow {BC} } \right) + \frac{1}{5}\overrightarrow {BC} = \dfrac{1}{6}\overrightarrow {AB} + \frac{1}{{30}}\overrightarrow {BC} \\
= \dfrac{1}{6}\left( {\overrightarrow {AB} + \dfrac{1}{5}\overrightarrow {BC} } \right)\\
\Rightarrow \overrightarrow {AH} = 6\overrightarrow {KH} \Rightarrow \overline {A,K,H}
\end{array}\)
