2(x-y)(x+y)-(x+y)的平方 (用提取公因式做,

问题描述:

2(x-y)(x+y)-(x+y)的平方 (用提取公因式做,

2(x-y)(x+y)-(x+y)2中可把(x+y)看成一个整体提取.所以2(x-y)(x+y)-(x+y)2=(x+y){2(x-y)-(X+Y)}=(x+y)(X-3Y)