\(\overrightarrow{AH}=\overrightarrow{AB}+\overrightarrow{BH}=\overrightarrow{AB}+\frac{1}{2}\overrightarrow{BC}=\frac{6\overrightarrow{AB}+3\overrightarrow{BC}}{6}\)
\(\overrightarrow{AK}=\overrightarrow{AB}+\overrightarrow{BK}=\overrightarrow{AB}+\frac{1}{6}\overrightarrow{BD}\)
\(\overrightarrow{AB}+\frac{1}{6}\left(\overrightarrow{BA}+\overrightarrow{BC}\right)\)
\(\frac{5}{6}\overrightarrow{AB}+\frac{1}{6}\overrightarrow{BC}=\frac{5\overrightarrow{AB}+\overrightarrow{BC}}{6}\)
\(\rightarrow\overrightarrow{AH}\ne k.\overrightarrow{AK}\left(k\ne0\right)\)
Nên A, K, H không thẳng hàng.
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