(x-2y)(x+2y)-(x-2y)²,其中x=-2,y=1/2.

问题描述:

(x-2y)(x+2y)-(x-2y)²,其中x=-2,y=1/2.

(x-2y)(x+2y)-(x-2y)²
=(x-2y)(x+2y-x+2y)
=4y(x-2y)
=2×(-2-1)
=-6