Tìm số phức z sao cho \(3z - \overline z = 2(3 - 10i)\).

Vu Phuong Thao

New member
Tìm số phức z sao cho \(3z - \overline z = 2(3 - 10i)\).
A. \(z = - 3 - 5i\)
B. \(z = - 3 + 5i\)
C. \(z = 3 - 5i\)
D. \(z = 3 + 5i\)
 

Hung Le

New member
\(\begin{array}{l} z = x + yi\,(x,y \in\mathbb{R} )\\ \Rightarrow \overline z = x - yi\\ 3z - \overline z = 2(3 - 10i)\\ \Leftrightarrow 3(x + iy) - (x - iy) = 6 - 20i\\ \Leftrightarrow 2x + 4yi = 6 - 20i\\ \Leftrightarrow \left\{ \begin{array}{l} 2x = 6\\ 4y = - 20 \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l} x = 3\\ y = - 5 \end{array} \right.\\ \Rightarrow z = 3 - 5i \end{array}\)