Xét $\Delta=(5-i)^2-4(8-i)=-8-6i$$\Rightarrow \delta=\sqrt{\Delta}=\pm(1-3i)$$\begin{cases}z_1= \dfrac{5-i+\delta}{2}=3-2i\\ z_2=\dfrac{5-i-\delta}{2}=2+i \end{cases}$
Xét $\Delta=(5-i)^2-4(8-i)=-8-6i$$\Rightarrow \delta
_{1,2}=\sqrt{\Delta}=\pm(1-3i)$$\begin{cases}z_1= \dfrac{5-i+\delta
_1}{2}=3-2i\\ z_2=\dfrac{5-i
+\delta
_2}{2}=2+i \end{cases}$