应该是题目有问题!(x+2y) 、 (x-2y)二者取其一.请补充说明先.（x+2y）(3x-7y)²-4(x+2y)(x+y)² 分解因式 打错了，sorry（x+2y）(3x-7y)²-4(x+2y)(x+y)²=（x+2y）[(3x-7y)²-4(x+y)²]=(x+2y)[(3x-7y)+2(x+y)]*[(3x-7y)-2(x+y)]=(x+2y)(5x-5y)(x-9y)=5(x+2y)(x-y)(x-9y)