求下列各式的值：x-1/2x²-2,其中x=-1/2; x²-4xy+4y²/2x-4y,其中x=-1,y=-1/2.

求下列各式的值：x-1/2x²-2,其中x=-1/2; x²-4xy+4y²/2x-4y,其中x=-1,y=-1/2.
求下列各式的值：x-1/2x²-2,其中x=-1/2; x²-4xy+4y²/2x-4y,其中x=-1,y=-1/2.

求下列各式的值：x-1/2x²-2,其中x=-1/2; x²-4xy+4y²/2x-4y,其中x=-1,y=-1/2.
x-1/2x²-2
=(x-1)/2(x²-1)
=（x-1）/2（x+1）（x-1）
=1/2(x+1)
=1/2(-2+1)
=-1/2
x²-4xy+4y²/2x-4y
=(x-2y)²/2(x-2y)
=1/2(x-2y)
=1/2x-y
=1/2x(-1)+1/2
=-1/2+1/2
=0
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