因式分解,
原式=(x+y)(x-y)-(x+y)^2=(x+y)(x-y-x-y)=-2y(x+y)
x²-y²-(x+y)²=(x+y)(x-y)-(x+y)²=(x+y)[(x-y)-(x+y)]=-2y(x+y)
原式=x²-y²-(x²+2xy+y²)=2xy-2y² 赞一个呗
以上分解的都正确