-½x²×(2xy²-4x²y²)-4x²y×(-xy)
=-x³y²(1-2x)+4x³y²
=3x³y²+2x^4y²
=3*1/4+2*1/4
=5/4
x³-2x[½x²-3(三分之一乘x-1)]
=x³-x³+2x(x-1)
=2x²+2x
=1/2-1
=-1/2
先化简,再求值.1.-½x²×(2xy²-4x²y²)-4x²y×(-xy) ,其中X=2Y=1.2.x³-2x[½x²
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