\[x^{4} + 20x^{2} + 64 = 0\]
\[x^{2} = y \geq 0:\]
\[y^{2} + 20y + 64 = 0\]
\[D_{1} = 100 - 64 = 36\]
\[y_{1} = - 10 + 6 = - 4 < 0;\ \]
\[y_{2} = - 10 - 6 = - 16 < 0.\]
\[Ответ:нет\ корней.\]