题目

(x-2y)²-2(x+2y)(x-2y)+(x+2y)²,其中x=1,y=2

提问时间：2020-10-23

答案

(x-2y)²-2(x+2y)(x-2y)+(x+2y)²= [ (x - 2y) - ( x + 2y)]²= [ x - 2y - x - 2y]²= ( -4y)² = 16y²把x = 1 ,y = 2代入上式得：原式 = 16 × 2² = 64