Cho số phức

A

- Hướng dẫn giải

Đáp án A

Gọi $z=x+yi,x,y\in ℝ$.

$$\begin{gathered} \left(1+i\right)z+2\overline{z}=1+2i \\ \iff \left(1+i\right)\left(x+yi\right)+2\left(x-yi\right)=1+2i \\ \iff x+yi+xi+y{i}^2+2x-2yi=1+2i \\ \iff \left(3x-y\right)+\left(x-y\right)i=1+2i \\ \iff \left\{\begin{array}{l}3x-y=1\\ x-y=2\end{array}\right. \\ \iff \left\{\begin{array}{l}x=-\frac{1}{2}\\ y=-\frac{5}{2}\end{array}\right.. \end{gathered}$$

Vậy P = -3