\[y = x^{4} - 8x^{2} - 9;\ \ \ \ y = 0\]
\[x^{4} - 8x^{2} - 9 = 0\]
\[Пусть\ x^{2} = a:\]
\[a^{2} - 8a - 9 = 0\]
\[a_{1} + a_{2} = 8;\ \ \ a_{1} \cdot a_{2} = - 9\]
\[a_{1} = 9;\ \ \ a_{2} = - 1\]
\[Подставим:\]
\[1)\ x^{2} = - 1\]
\[нет\ корней.\]
\[2)\ x^{2} = 9\]
\[x = \pm 3.\]
\[Ответ:\ \ (3;0);\ \ ( - 3;0).\]