(y-x)(a-b-c)+(x-y)(b-a-c)
问题描述:
(y-x)(a-b-c)+(x-y)(b-a-c)
答
原式=(y-x)(a-b-c)-(y-x)(b-a-c)
=(y-x)(a-b-c-b+a+c)
=2(y-x)(a-b).