TeX джерело:

\frac{{\frac{x}{y} - \frac{y}{x}}}{{\frac{x}{y} + \frac{y}{x} - 2}} = \frac{{\frac{{{x^2} - {y^2}}}{{xy}}}}{{\frac{{{x^2} + {y^2} - 2xy}}{{xy}}}} = \frac{{(x - y)(x + y)}}{{xy}} \cdot \frac{{xy}}{{{{(x - y)}^2}}} = \frac{{(x - y)(x + y)xy}}{{xy(x - y)(x - y)}} = \frac{{x + y}}{{x - y}}