TeX джерело:

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