Trong không gian Oxyz, cho hai...

Câu hỏi: Trong không gian Oxyz, cho hai vectơ $\overrightarrow{\mathrm{u}}$ = (x; y; z), $\overrightarrow{\mathrm{v}}$ = (x'; y'; z'). Khẳng định nào dưới đây sai?

A. $\left|\overrightarrow{\mathrm{u}}\right|=\sqrt{{\mathrm{x}}^2+{\mathrm{y}}^2+{\mathrm{z}}^2}$

B. $\overrightarrow{\mathrm{u}}+\overrightarrow{\mathrm{v}}=\left(\mathrm{x}+\mathrm{x}\text{'};\mathrm{y}+\mathrm{y}\text{'};\mathrm{z}+\mathrm{z}\text{'}\right)$

C. $\overrightarrow{\mathrm{u}}.\overrightarrow{\mathrm{v}}=\left(\mathrm{x}+\mathrm{y}+\mathrm{z}\right).\left(\mathrm{x}\text{'}+\mathrm{y}\text{'}+\mathrm{z}\text{'}\right)$

D. $\overrightarrow{\mathrm{u}}\perp \overrightarrow{\mathrm{v}}\iff \mathrm{x}.\mathrm{x}\text{'}+\mathrm{y}.\mathrm{y}\text{'}+\mathrm{z}.\mathrm{z}\text{'}=0$