#(x^2-y^2)/(xy+x^2) div (y-x)/(x+y)#
#color(white)("XXXX")##= (x^2-y^2)/(xy+x^2) * (x+y)/(y-x)#
#color(white)("XXXX")##=((x+y)(x-y))/(x(x+y))*(x+y)/((-1)(x-y))#
#color(white)("XXXX")##=(cancel((x+y))cancel((x-y)))/(xcancel((x+y)))*(x+y)/((-1)cancel((x-y)))#
#color(white)("XXXX")##= -(x+y)/x#