\[\left( x - \frac{x - 1}{x} \right)^{2} - \left( x + \frac{x - 1}{x} \right)^{2} =\]
\[= \left( x - \frac{x - 1}{x} - x - \frac{x - 1}{x} \right) \cdot \left( x - \frac{x - 1}{x} + x + \frac{x - 1}{x} \right) =\]
\[= \frac{- x + 1 - x + 1}{x} \cdot 2x = (2 - 2x) \cdot 2 =\]
\[= 4 - 4x\]