\[x^{4} - 29x^{2} + 100 = 0\]
\[x^{2} = t \geq 0:\]
\[t^{2} - 29t + 100 = 0\]
\[t_{1} + t_{2} = 29;\ \ t_{1} \cdot t_{2} = 100\]
\[t_{1} = 25;\ \ t_{2} = 4.\]
\[1)\ x^{2} = 25\]
\[x = \pm 5.\]
\[2)\ x^{2} = 4\]
\[x = \pm 2.\]
\[Ответ:x = \pm 2;x = \pm 5.\]