(x - 1)² - 2 . 3 = -2
⇒ (x - 1)² - 6 = -2
⇒ (x - 1)² = -2 + 6
⇒ (x - 1)² = 4
⇒ \(\left[ \begin{array}{l}(x-1)²=2²\\(x-1)²=(-2)²\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x-1=2\\x-1=-2\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=2+1\\x=-2+1\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=3\\x=-1\end{array} \right.\)
Vậy x ∈ {3; -1}