Simplify: xy−yxxy+yx\frac{\frac{x}{y} - \frac{y}{x}}{\frac{x}{y} + \frac{y}{x}}yx+xyyx−xy
x2−y2x2+y2\frac{x^2-y^2}{x^2+y^2}x2+y2x2−y2
x−yx+y\frac{x-y}{x+y}x+yx−y
111
x2+y2x2−y2\frac{x^2+y^2}{x^2-y^2}x2−y2x2+y2