2. (5 分) 设复数 $z_{1}, z_{2}$ 在复平面内的对应点关于虚轴对称, $z_{1}=2+i$, 则 $z_{1} z_{2}=$
Gaokao · Math · previous-year question
- A.-5
- B.5
- C.$-4+i$
- D.$-4-i$
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