xy-2y²-2[4xy-（3y²-x²y）+5（-3y²+2/5 x²y）],其中x=1,y=-2．

xy-2y²-2[4xy-（3y²-x²y）+5（-3y²+2/5 x²y）],其中x=1,y=-2．
xy-2y²-2[4xy-（3y²-x²y）+5（-3y²+2/5 x²y）],其中x=1,y=-2．

xy-2y²-2[4xy-（3y²-x²y）+5（-3y²+2/5 x²y）],其中x=1,y=-2．
xy-2y²-2[4xy-（3y²-x²y）+5（-3y²+2/5 x²y）]
=xy-2y²-2(4xy-3y²+x²y-15y²+2x²y)
=xy-2y²-2(4xy-18y²+3x²y)
=xy-2y²-8xy+36y²-6x²y
=y(x-2y-8x+36y-6x²)
=-2(1+4-8-72-6)
=162

xy-2y²-2[4xy-（3y²-x²y）+5（-3y²+2/5 x²y）]
=xy-2y²-2[4xy-3y²+x²y-15y²+2x²y]
=xy-2y²-2[4xy-3y²-15y²+x²y+2x²y]
=xy-2y&...

全部展开

xy-2y²-2[4xy-（3y²-x²y）+5（-3y²+2/5 x²y）]
=xy-2y²-2[4xy-3y²+x²y-15y²+2x²y]
=xy-2y²-2[4xy-3y²-15y²+x²y+2x²y]
=xy-2y²-2[4xy-18y²+3x²y]
=xy-2y²-8xy+36y²-6x²y
=xy-8xy-2y²+36y²-6x²y
=-7xy+34y²-6x²y
=-7*1*(-2)+34*(-2)²-6*1²*(-2)
=14+136+12
=162

收起

xy-2y²-2[4xy-（3y²-x²y）+5（-3y²+2/5 x²y）]
=xy-2y²-2[4xy-3y²+x²y-15y²+2x²y]
=xy-2y²-2(4xy-18y²+3x²y)
=xy-2y²-8xy+36y²-6x²y
=34y²-7xy-6x²y
=34×4+7×1×2+6×1×2
=136+26
=162