1) (x+y)(x+y) -4xy) /(x+y) = (x² +2xy +y² -4xy) /(x +y) =(x² -2xy +y²) /(x +y) =(x -y)² / (x +y)
2) (y-x)(y-x)+4xy) /(y-x) = (y² -2xy +x² +4xy) / -(x-y) = (y² +2xy +x²) / -(x -y) =(x +y)² / -(x -y)
3) ((x-y)² *(x+y)²) /-(x+y)*(x-y) = -(x-y)(x+y) = -(x² -y²) = y² -x²