Cho \(\vec a=(1;0;-3), \vec b=(2;1;2)\). Khi đó \(...

C

- Hướng dẫn giải

\(\begin{array}{l} \left[ {\overrightarrow a ,\overrightarrow b } \right] = \left( {\left| {\begin{array}{*{20}{c}} 0&{ - 3}\\ 1&2 \end{array}} \right|;\left| {\begin{array}{*{20}{c}} { - 3}&1\\ 2&2 \end{array}} \right|;\left| {\begin{array}{*{20}{c}} 1&0\\ 2&1 \end{array}} \right|} \right) = \left( {3; - 8;1} \right)\\ \Rightarrow \left| {\left[ {\overrightarrow a ,\overrightarrow b } \right]} \right| = \sqrt {9 + 64 + 1} = \sqrt {74} \end{array}\)