求代数式2x^2y+{2xy-[3x^2y-2(-3x^2y+2xy)]-4xy^2},其中x=-1/2 y=2
题目
求代数式2x^2y+{2xy-[3x^2y-2(-3x^2y+2xy)]-4xy^2},其中x=-1/2 y=2
答案
2x^2y+{2xy-[3x^2y-2(-3x^2y+2xy)]-4xy^2}
=2x^2y+{2xy-[3x^2y+6x^2y-4xy]-4xy^2}
=2x^2y+{2xy-3x^2y-6x^2y+4xy-4xy^2}
=2x^2y+2xy-3x^2y-6x^2y+4xy-4xy^2
=-7x^2y+6xy-4xy^2
=xy(-7x+6-4y)
=(-1/2)*2*[-7*(-1/2)+6-4*2]
=-(7/2+6-8)
=-(7/2-2)
=-3/2
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