\(-2x^2-8x+2=0\)
\(< =>-\left(\left(\sqrt{2}x\right)+2.\sqrt{2}x.\frac{4}{\sqrt{2}}+8\right)+8+2=0\)
\(< =>\sqrt{10}^2-\left(\sqrt{2}x+8\right)^2=0\)
\(< =>\left(\sqrt{10}-\sqrt{2}x-8\right)\left(\sqrt{10}+\sqrt{2}x+8\right)=0\)
\(< =>\orbr{\begin{cases}-\sqrt{2}x=8-\sqrt{10}\\\sqrt{2}x=-8-\sqrt{10}\end{cases}< =>\orbr{\begin{cases}x=\frac{\sqrt{10}-8}{\sqrt{2}}\\x=\frac{-\sqrt{10}-8}{\sqrt{2}}\end{cases}}}\)