Cho ba vectơ vecto a=(3;-1;-2), vecto b (1;2;m), vecto c=(5,1,7). Xác

Câu hỏi :

Cho ba vectơ $\stackrel{\rightharpoonup }{a}=\left(3;-1;-2\right)$, $\stackrel{\rightharpoonup }{b}=\left(1;2;m\right)$, $\stackrel{\rightharpoonup }{c}=\left(5;1;7\right)$. Xác định m để $\stackrel{\rightharpoonup }{c}=\left[\stackrel{\rightharpoonup }{a},\stackrel{\rightharpoonup }{b}\right]$