(a+b-c-d)*(a-b-c+d)=[(___)+(___)]*[(___)-(___)]?括号内填什么?

问题描述:

(a+b-c-d)*(a-b-c+d)=[(___)+(___)]*[(___)-(___)]?括号内填什么?

(a+b-c-d)*(a-b-c+d)=[(a-c)+(b-d)]*[(a-c)-(b-d)]
=(a-c)²-(b-d)²
=a²-2ac+c²-b²+2bd-d²