化简求值3x²y-[2xy²-2(xy-3/2x²y)+xy]+3xy²其中x=3、y=-1/3
问题描述:
化简求值3x²y-[2xy²-2(xy-3/2x²y)+xy]+3xy²其中x=3、y=-1/3
急用呀
答
3/2x²y=(3/2)x²y
3x²y-[2xy²-2(xy-(3/2)x²y)+xy]+3xy²
=3x²y-[2xy²-2xy+3x²y+xy]+3xy²
=3x²y-2xy²+2xy-3x²y-xy+3xy²
=xy²+xy
=xy(y+1)
=3*(-1/3)*(-1/3+1)
=-2/3