(x-1)² = 5²
⇒ \(\left[ \begin{array}{l}x-1= 5\\x-1= -5\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=6\\x=-4\end{array} \right.\)
Vậy x ∈ { 6 ; -4}
$\frac{x}{-15}$ = $\frac{-60}{x}$
⇒ x.x = -15 . (-60)
⇒ x² = 900
⇒ x² = 30²
⇒\(\left[ \begin{array}{l}x=30\\x=-30\end{array} \right.\)
Vậy x ∈ {30;-30}