Question

Resolva,em R,a aquação $x^{4}$ -5$x^{2}$ - 14 = 0

Answer 1

Olá Manusb,
boa noite!

$x^4-5x^2-14=0\\\underbrace{(x^2-7)}_{I}\cdot\underbrace{(x^2+2)}_{II}=0\\\begin{cases}I:\;\;x^2-7\Rightarrow\,x^2=7\Rightarrow\boxed{x=\pm\sqrt{7}}\\II:\;\;x^2+2=0\Rightarrow\,x^2=-2\end{cases}\\\\\text{Logo,}\;\;\boxed{\boxed{S=\left\{-\sqrt{7},\sqrt{7}\right\}}}$