\[\boxed{\mathbf{637}.}\]
\[1)\ \sqrt[3]{x} = x^{2} + x - 1\]
\[f(x) = \sqrt[3]{x};\ \ \ \ \]
\[g(x) = x^{2} + x - 1\]
\[x = \pm 1.\]
\[2)\ x^{- 2} = 2x^{2} - 1\]
\[f(x) = x^{- 2};\ \ \ g(x) = 2x^{2} - 1\]