已知:A=-x²+2xy-y²,Bxy-3x²,C=2y²-xy,求A-2B+3C
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![已知:A=-x²+2xy-y²,Bxy-3x²,C=2y²-xy,求A-2B+3C](/uploads/image/z/695967-15-7.jpg?t=%E5%B7%B2%E7%9F%A5%EF%BC%9AA%3D-x%26%23178%3B%2B2xy-y%26%23178%3B%2CBxy-3x%26%23178%3B%2CC%3D2y%26%23178%3B-xy%2C%E6%B1%82A-2B%2B3C)
已知:A=-x²+2xy-y²,Bxy-3x²,C=2y²-xy,求A-2B+3C
已知:A=-x²+2xy-y²,Bxy-3x²,C=2y²-xy,求A-2B+3C
已知:A=-x²+2xy-y²,Bxy-3x²,C=2y²-xy,求A-2B+3C
A-2B+3C
=(-x²+2xy-y²)-2(xy-3x²)+3(2y²-xy)
=-x²+2xy-y²-2xy+6x²+6y²-3xy
=5x²-3xy+5y²