Tìm x biết rằng: x^2 - 6x + 8 = 0

* Hướng dẫn giải

$\begin{array}{l}{x}^2-6x+8=0\\ x^2-2x-4x+8=0\\ x\left(x-2\right)-4\left(x-2\right)=0\\ \left(x-4\right)\left(x-2\right)=0\\ \Rightarrow \left[\begin{array}{l}x-4=0\\ x-2=0\end{array}\right.\\ \Rightarrow \left[\begin{array}{l}x=4\\ x=2\end{array}\right.\end{array}$

Vậy $x\in \left\{2;4\right\}$