已知xy²=-2,求-xy(x³y七次方-3x²y五次方-y)
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![已知xy²=-2,求-xy(x³y七次方-3x²y五次方-y)](/uploads/image/z/1818917-53-7.jpg?t=%E5%B7%B2%E7%9F%A5xy%26sup2%3B%3D-2%2C%E6%B1%82-xy%28x%26sup3%3By%E4%B8%83%E6%AC%A1%E6%96%B9-3x%26sup2%3By%E4%BA%94%E6%AC%A1%E6%96%B9-y%29)
已知xy²=-2,求-xy(x³y七次方-3x²y五次方-y)
已知xy²=-2,求-xy(x³y七次方-3x²y五次方-y)
已知xy²=-2,求-xy(x³y七次方-3x²y五次方-y)
-xy(x³y七次方-3x²y五次方-y)
=-xy[(x³y^6)y-3(x²y^4)y-y]
=-xy[(xy²)³y-3(xy²)²y-y]
=-xy[(-2)³y-3(-2)²y-y]
=-xy(-8y-12y-y)
=21xy²
=21×(-2)
=-42