Question

Vectơ AC + vectơ CD - vectơ EC = vectơ AE - vectơ DB + vectơ CB 

Answer 1

\(\overrightarrow{AC}+\overrightarrow{CD}-\overrightarrow{EC}=\overrightarrow{AE}-\overrightarrow{DB}+\overrightarrow{CB}\left(1\right)\)

\(\Leftrightarrow\overrightarrow{AD}+\overrightarrow{DB}=\overrightarrow{AE}+\overrightarrow{EC}+\overrightarrow{CB}\)

\(\Leftrightarrow\overrightarrow{AB}=\overrightarrow{AC}+\overrightarrow{CB}\)

\(\Leftrightarrow\overrightarrow{AB}=\overrightarrow{AB}\left(đúng\right)\)

Vậy \(\left(1\right)đpcm\)