Question

????????
$- 2 {x}^{2} - 800 = 0$
​

Answer 1

$-2x^2-800~=~0\\\\\\-2x^2~=~800\\\\\\x^2~=~\frac{800}{-2}\\\\\\x^2~=~-400\\\\\\\boxed{x~=~\pm\sqrt{-400}~~~\rightarrow~~~Nao~h\acute{a}~solucaoes~Reais}$

No entanto, caso já tenha iniciado seus estudos sobre o conjunto dos numero complexos, temos:

$x~=~\pm\sqrt{-400}\\\\\\x~=~\pm\sqrt{400~.~-1}\\\\\\x~=~\pm\sqrt{400}\,.\,\sqrt{-1}\\\\\\\boxed{x~=~\pm20i}~~~ou~~~\boxed{x\in\mathbb{C}\,/\,x=-20i~ou~x=20i}$