更新时间2018-03-12 08:17:38
(x-y)(a+b)-(x-y)(a-b)
=(x-y)(a+b-a+b)
=(x-y)*2b
=2b(x-y)
应该是:(x-y)(a+b)-(x-y)(a-b)
=(x-y)[a+b-(a-b)]
=(x-y)(a+b-a+b)
=2b(x-y)
(x-y)(a+b)-(x-y)(a-b)
=(x-y)[(a+b)-(a-b)]
=(x-y)(a+b-a+b)
=(x-y)*2b
=2bx-2by
原式=(x-y)[(a+b)-(a-b)]
=(x-y)(a+b-a+b)
=2b(x-y)
(x-y)(a+b)—(x—y)(a—b)
=(x-y)【a+b-(a-b)】
=(x-y)(a+b-a+b)
=2b(x-y)