3xy²-2(xy-3/2x²y)+(3x²y-2xy²),其中,x=-2,y=
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3xy²-2(xy-3/2x²y)+(3x²y-2xy²),其中,x=-2,y=1/2
挺急的,答对再追加10、
先化简,再求值
挺急的,答对再追加10、
先化简,再求值
解原式
=3xy²-2(xy-3/2x²y)+(3x²y-2xy²)
=3xy²-2xy+3x²y+3x²y-2xy²
=xy²+6x²y-2xy
=xy(y+6x-2)
=(-2)×(1/2)[1/2+6×(-2)-2]
=-(1/2-14)
=14-1/2
=27/2
再问: 还有一题,已知2x-3y=1,试求(2x²+4x-3y)+2(-x²+x-3y)-17的值。
再答: 解由(2x²+4x-3y)+2(-x²+x-3y)-17
=(2x²+4x-3y)+(-2x²+2x-6y)-17
=6x-9y-17
=3(2x-3y)-17
=3*1-17
=-14.
=3xy²-2(xy-3/2x²y)+(3x²y-2xy²)
=3xy²-2xy+3x²y+3x²y-2xy²
=xy²+6x²y-2xy
=xy(y+6x-2)
=(-2)×(1/2)[1/2+6×(-2)-2]
=-(1/2-14)
=14-1/2
=27/2
再问: 还有一题,已知2x-3y=1,试求(2x²+4x-3y)+2(-x²+x-3y)-17的值。
再答: 解由(2x²+4x-3y)+2(-x²+x-3y)-17
=(2x²+4x-3y)+(-2x²+2x-6y)-17
=6x-9y-17
=3(2x-3y)-17
=3*1-17
=-14.
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