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