先化简,再求值:(x-½y-1)（x-½y+1）-(x-½y-1)²,其中x=5,y=3.
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先化简,再求值:(x-½y-1)（x-½y+1）-(x-½y-1)²,其中x=5,y=3.
:(x-½y-1)（x-½y+1）-(x-½y-1)²
=(x-½y-1)[(x-½y+1)-(x-½y-1)]
=2(x-½y-1)
=2x-y-2
x=5,y=3时
原式=2×5-3-2=5
先化简,再求值:(x-½y-1)（x-½y+1）-(x-½y-1)²,其中x=5,y=3.
:(x-½y-1)（x-½y+1）-(x-½y-1)²
=(x-½y-1)[(x-½y+1)-(x-½y-1)]
=2(x-½y-1)
=2x-y-2
x=5,y=3时
原式=2×5-3-2=5