Решите уравнение: x^4-3x^2-4=0.

\[x^{4} - 3x^{2} - 4 = 0\]

\[t = x^{2},\ \ \ t \geq 0\]

\[t^{2} - 3t - 4 = 0\]

\[D = ( - {3)}^{2} - 4 \cdot 1 \cdot ( - 4) =\]

\[= 9 + 16 = 25\]

\[t_{1} = \frac{3 + \sqrt{25}}{2} = \frac{2 + 5}{2} = \frac{8}{2} = 4\]

\[t_{2} = \frac{3 - \sqrt{25}}{2} = \frac{3 - 5}{2} = \frac{- 2}{2} =\]

\[= - 1\ (не\ подходит).\]

\[x^{2} = 4\]

\[x = \pm 2\]

\[Ответ:2;\ - 2.\]