(2x²y-3xy²)-3(x²y-2xy²)+2(x²y-4xy
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(2x²y-3xy²)-3(x²y-2xy²)+2(x²y-4xy²),其中x=-1,y=2.
先化简,后求值,
先化简,后求值,
(2x²y-3xy²)-3(x²y-2xy²)+2(x²y-4xy²)
=2x²y-3xy²-3x²y+6xy²+2x²y-8xy²
=x²y-5xy²
=xy(x-5y)
将x=-1,y=2.代入得
原式=-2×(-1-10)=22
=2x²y-3xy²-3x²y+6xy²+2x²y-8xy²
=x²y-5xy²
=xy(x-5y)
将x=-1,y=2.代入得
原式=-2×(-1-10)=22
3x²y+xy²-[2xy²-4x²y+(x²y-2xy²)
(2x²y-3xy²)-3(x²y-2xy²)+2(x²y-4xy
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