先化简再求值3x²y-[2xy²-2(xy-3/2 x²y)]+3xy²,其中x=3 y= -1/3
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先化简再求值3x²y-[2xy²-2(xy-3/2 x²y)]+3xy²,其中x=3 y= -1/3
先化简再求值3x²y-[2xy²-2(xy-3/2 x²y)]+3xy²,其中x=3 y= -1/3
先化简再求值3x²y-[2xy²-2(xy-3/2 x²y)]+3xy²,其中x=3 y= -1/3
3x²y-[2xy²-2(xy-3/2 x²y)]+3xy²
=3x²y-(2xy²-2xy+3x²y)+3xy²
=3x²y-2xy²+2xy-3x²y+3xy²
=-2xy²+2xy+3xy²
=xy²+2xy
=xy(y+2) x=3,y=-1/3
=-1(-1/3+2)
=-5/3
3x²y-[2xy²-2(xy-3/2 x²y)]+3xy²
=3x²y-(2xy²-2xy+3 x²y)+3xy²
=3x²y-2xy²+2xy-3 x²y+3xy²
=xy²+2xy
=xy(y+2)
x=3 y= -1/3 y=-1/9
x、y代进去得17/243