计算 (1)(x-y)2-(y+2x)(y-2x) (2)a2-4a+4-b2

问题描述:

计算
(1)(x-y)2-(y+2x)(y-2x)          (2)a2-4a+4-b2

(1)原式=x2-2xy+y2-(y2-4x2)(2分)
=x2-2xy+y2-y2+4x2
=5x2-2xy(4分)
(2)原式=(a-2)2-b2(2分)
=(a+b-2)(a-b-2)(4分)