Question

Cho hình hộp ABCD.A'B'C'D'. Chứng minh rằng:

a) \(\overrightarrow{AB}+\overrightarrow{B'C'}+\overrightarrow{DD'}=\overrightarrow{AC'}\);

b) \(\overrightarrow{DB'}+\overrightarrow{D'D}+\overrightarrow{BD'}=\overrightarrow{BB'}\);

c) \(\overrightarrow{AC}+\overrightarrow{BA'}+\overrightarrow{DB}+\overrightarrow{C'D}=\overrightarrow{0}\).