化简：4ab+8-2b²-9ab-6= (2)先化简,再求值：3x²y-[2x²y-3(2xy-x²y)-xy]其中x=-1,y=-2

化简：4ab+8-2b²-9ab-6= (2)先化简,再求值：3x²y-[2x²y-3(2xy-x²y)-xy]其中x=-1,y=-2
化简：4ab+8-2b²-9ab-6= (2)先化简,再求值：
3x²y-[2x²y-3(2xy-x²y)-xy]其中x=-1,y=-2

化简：4ab+8-2b²-9ab-6= (2)先化简,再求值：3x²y-[2x²y-3(2xy-x²y)-xy]其中x=-1,y=-2
（1）4ab+8-2b²-9ab-6
= - 5ab - 2b²+2
（2）3x²y-[2x²y-3(2xy-x²y)-xy]
=3x²y-2x²y+3(2xy-x²y)+xy
=x²y+6xy-3x²y+xy
=-2x²y+7xy（把x和y的值代入即可）
=4+14
=18

4ab+8-2b²-9ab-6=-5ab-2b²+2
原式=3x²y-2x²y+3(2xy-x²y)+xy
=x²y+6xy-3x²y+xy
=-2x²y+7xy
=4+14
=18

1 -5ab-2b²+2
2 18