$\begin{align}  & {{({{x}^{2}}-1)}^{2}}-2({{x}^{2}}-1)-3=0\xrightarrow{{{x}^{2}}-1=t}{{t}^{2}}-2t-3=0 \\  & \Rightarrow (t+1)(t-3)=0\left\{ \begin{matrix}   t=-1\Rightarrow {{x}^{2}}-1=-1\Rightarrow {{x}^{2}}=0\Rightarrow x=0  \\   t=3\Rightarrow {{x}^{2}}-1=3\Rightarrow {{x}^{2}}=4\Rightarrow x=\pm 2  \\\end{matrix} \right. \\ \end{align}$