(4xy/(y^2-x^2) : (1/(y^2-x^2)+1/(x^2+2xy+y^2))= =(4xy/(y^2-x^2) : (1/((y-x)(y+x))+1/(y+x)^2)= =4xy/(y^2-x^2) : ((y-x+y+x)/((y+x)^2*(y-x))= =4xy/(y^2-x^2) 2y/((y+x)^2*(y-x))= =(4xy*(y+x)^2*(y-x))/(2y*(y^2-x^2))= =2x*(y+x)^2*(y-x))/((y-x)(y+x))= 2x(y+x)