Question

xy-x+y-y²x²-y²  решить

Answer 1

$frac{xy-x+y-y^2}{x^2-y^2}=frac{x(y-1)+y(1-y)}{(x-y)(x+y)}=\\ =frac{x(y-1)-y(y-1)}{(x-y)(x+y)}=frac{(x-y)(y-1)}{(x-y)(x+y)}=frac{y-1}{x+y}.$