先化简,再求值:3x²y-[2x²y-(xy²-x²y)-4xy²],其中x=-2,y=1/2
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![先化简,再求值:3x²y-[2x²y-(xy²-x²y)-4xy²],其中x=-2,y=1/2](/uploads/image/z/5558715-27-5.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%86%8D%E6%B1%82%E5%80%BC%3A3x%26%23178%3By-%5B2x%26%23178%3By-%28xy%26%23178%3B-x%26%23178%3By%29-4xy%26%23178%3B%5D%2C%E5%85%B6%E4%B8%ADx%3D-2%2Cy%3D1%2F2)
先化简,再求值:3x²y-[2x²y-(xy²-x²y)-4xy²],其中x=-2,y=1/2
先化简,再求值:3x²y-[2x²y-(xy²-x²y)-4xy²],其中x=-2,y=1/2
先化简,再求值:3x²y-[2x²y-(xy²-x²y)-4xy²],其中x=-2,y=1/2
3x²y-[2x²y-(xy²-x²y)-4xy²],其中x=-2,y=1/2
=3x²y-2x²y+xy²-x²y+4xy²
=5xy²
=5×(-1)×1/4
=-5/2;
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3x²y-[2x²y-(xy²-x²y)-4xy²]
=3x²y-2x²y+(xy²-x²y)+4xy²
=5xy²
代入x=-2,y=1/2
5xy²=5*(-2)*(1/2)²=-5/2
3x²y-[2x²y-(xy²-x²y)-4xy²]
=3x²y-2x²y+xy²-x²y+4xy²
=5xy²
=5*(-2)*1/4
=-5/2