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
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![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](/uploads/image/z/5437260-36-0.jpg?t=%E5%8C%96%E7%AE%80%EF%BC%9A4ab%2B8-2b%26%23178%3B-9ab-6%3D+%282%29%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%86%8D%E6%B1%82%E5%80%BC%EF%BC%9A3x%26%23178%3By-%5B2x%26%23178%3By-3%282xy-x%26%23178%3By%29-xy%5D%E5%85%B6%E4%B8%ADx%3D-1%2Cy%3D-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