先化简,再求值:(x-0.5y-1)(x-0.5y+1)-(x-0.5y-1)^2,其中x=5,y=3
问题描述：
先化简,再求值:(x-0.5y-1)(x-0.5y+1)-(x-0.5y-1)^2,其中x=5,y=3
答
(x-0.5y-1)(x-0.5y+1)-(x-0.5y-1)^2=[(x-0.5y)-1][(x-0.5y)+1]-[(x-0.5y)-1]^2=(x-0.5y)^2-1-[(x-0.5y)^2-2(x-0.5y)+1]=(x-0.5y)^2-1-(x-0.5y)^2+2(x-0.5y)-1=2(x-0.5y)-2将x=5,y=3代入上式(x-0.5y-1)(x-0.5y+1)-(x-...