先化简再求值 (x-½y-1)(x-½y+1)-(x-½y-1)²,其中 x=1.5 y=3.9
问题描述:
先化简再求值 (x-½y-1)(x-½y+1)-(x-½y-1)²,其中 x=1.5 y=3.9
答
(x-½y-1)(x-½y+1)-(x-½y-1)²
=(x-½y-1)[(x-½y+1)-(x-½y-1)]
=(x-½y-1)(x-½y+1-x+½y+1)
=2(x-½y-1)
x=1.5 y=3.9,
(x-½y-1)(x-½y+1)-(x-½y-1)²
=2(1.5-1/2*3.9-1)
=-3.9