\[ \bbox[#99CCFF,10px] {\Delta =b^{2}-4ac} \]

\[ \begin{align} & \Delta =2^{2}-4.8.(-1)\\ & \Delta =4+32\\ & \Delta=36 \end{align} \]

\[ \bbox[#99CCFF,10px] {x_{1,2}=\frac{-b\pm \sqrt{\Delta \;}}{2a}} \]

\[ \begin{align} & x_{1,2}=\frac{-2\pm\sqrt{36\;}}{2.8}\\ & x_{1,2}=\frac{-2\pm6}{16}\\ & x_{1}=\frac{-2+6}{16}=\frac{4:4}{16:4}=\frac{1}{4}\\ & x_{2}=\frac{-2-6}{16}=\frac{-8:8}{16:8}=-{\frac{1}{2}} \end{align} \]

\[ \bbox[#FFCCCC,10px] {V=\left\{\frac{1}{4},-\frac{1}{2}\right\}} \]