Cho

D

- Hướng dẫn giải

Đáp án D

$$\begin{gathered} P={\left|1-\overline{z_1}{z}_2\right|}^2-{\left|z_1-z_2\right|}^2=\left(1-\overline{z_1}.z_2\right)\overline{1-\overline{z_1}{z}_2}-\left(z_1-z_2\right)\overline{z_1-z_2} \\ =\left(1-\overline{z_1}.z_2\right)\left(1-z_1.\overline{z_2}\right)-\left(z_1-z_2\right)\left(\overline{z_1}-\overline{z_2}\right)=1-{\left|z_1\right|}^2-{\left|z_2\right|}^2+{\left|z_1\right|}^2.{\left|z_2\right|}^2=\left(1-{\left|z_1\right|}^2\right)\left(1-{\left|z_2\right|}^2\right) \end{gathered}$$

Dễ thấy $\left|z_1\right|=\left|z_2\right|=1$ suy ra  $P={\left|1-\overline{z_1}.z_2\right|}^2-{\left|z_1-z_2\right|}^2=0$.