Câu 1: \(\overrightarrow{AD}-\overrightarrow{CD}+\overrightarrow{CB}-\overrightarrow{DB}\)
\(=\overrightarrow{AD}+\overrightarrow{DC}+\overrightarrow{CB}+\overrightarrow{BD}\)
\(=\overrightarrow{AC}+\overrightarrow{CD}=\overrightarrow{AD}\)
=>Chọn B
Câu 2: C
Câu 3: B
Câu 4: \(\overrightarrow{a}=3\overrightarrow{i}-\overrightarrow{j}\)
=>\(\overrightarrow{a}=\left(3;-1\right)\)
\(\overrightarrow{b}=-\overrightarrow{i}+2\overrightarrow{j}\)
=>\(\overrightarrow{b}=\left(-1;2\right)\)
\(\overrightarrow{a}+\overrightarrow{b}=\left(3-1;-1+2\right)\)
=>\(\overrightarrow{a}+\overrightarrow{b}=\left(2;1\right)\)
=>Chọn D
Đúng 2
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