Question

(х-у/х+у - х+у/х-у):4/х^2-у^2.

Answer 1

$( frac{x-y}{x+y} - frac{x+y}{x-y}): frac{4}{x^2-y^2} =( frac{(x-y)^2-(x+y)&2}{x^2-y^2})* frac{x^2-y^2}{4} = frac{(x-y)^2-(x+y)&2}{4}}=$$frac{x^2-2xy+y^2-x^2-2xy-y^2}{4} = -frac{4xy}{4}=-xy$