\[y = f(x);\ \ \ y = g(x);\ \]
\[\ где\ \ f(x) = \frac{4}{x};\ \ \ g(x) = \frac{1}{x}\]
\[f(x + 1) - g\left( x^{2} - 1 \right) = 4\]
\[4x - 4 - 1 = 4x^{2} - 4\]
\[- 4x^{2} + 4x - 1 = 0\]
\[4x^{2} - 4x + 1 = 0\]
\[(2x - 1)^{2} = 0\]
\[x = \frac{1}{2}\]
\[Ответ:x = \frac{1}{2}\text{.\ }\]