已知(a+b)*(c-d)=ac-ad+bc-bd 试求(a-b)²=?

问题描述:

已知(a+b)*(c-d)=ac-ad+bc-bd 试求(a-b)²=?

(a-b)²=
=a²-2ab+b²

(a-b)²
=(a-b)*(a-b)
=aa-ab-ab+bb
=a²-2ab+b²