Đáp án:
$a) x-10=0$
$⇔x=10$
Vậy $x=10$
$b) 2x(x-2) -2x² =18$
$⇔2x^2 -4x -2x^2=18$
$⇔-4x=18$
$⇔-4x=18$
$⇔x=18 : (-4)$
$⇔x=-\dfrac{9}{2}$
Vậy $x=-\dfrac{9}{2}$
$c) (x-2)^2 -16=0$
$⇔(x-2-4)(x-2+4)=0$
$⇔(x-6)(x+2)=0$
$⇔$\(\left[ \begin{array}{l}x-6=0\\x+2=0\end{array} \right.\)
$⇔$\(\left[ \begin{array}{l}x=6\\x=-2\end{array} \right.\)
$\text{Vậy x ∈ {6 ; -2}}$
$d) x^3+4x=0$
$⇔x(x^2+4)=0$
Vì $x^2 ≥ 0$ nên $x^2+4 > 0$ (loại)
$⇔x=0$
Vậy $x=0$