Cho 2 vectơ \(\overrightarrow{u}=(1;2;-1);\,\,\ove...

B

- Hướng dẫn giải

Ta có:

\(\left[ \overrightarrow{u},\overrightarrow{v} \right]=(2x-3;x+1;-5)\)

Do đó

\(\left| \left[ \overrightarrow{u},\overrightarrow{v} \right] \right|=\sqrt{{{(2x-3)}^{2}}+{{(x+1)}^{2}}+25}=30 \\\Leftrightarrow 5{{x}^{2}}-10x+5=0\Leftrightarrow x=1.\)