\[n^{4} - 2n^{2} + 1 = 0\]
\[\left( n^{2} - 1 \right)^{2} = 0\]
\[n^{2} - 1 = 0\]
\[n^{2} = 1\]
\[n = \pm 1.\]
\[Ответ:n = \pm 1.\]