已知x+y=3,x²+y²-3xy=4, yx^3+xy^3=_____
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![已知x+y=3,x²+y²-3xy=4, yx^3+xy^3=_____](/uploads/image/z/8561520-0-0.jpg?t=%E5%B7%B2%E7%9F%A5x%2By%3D3%2Cx%26%23178%3B%2By%26%23178%3B-3xy%3D4%2C+yx%5E3%2Bxy%5E3%3D_____)
已知x+y=3,x²+y²-3xy=4, yx^3+xy^3=_____
已知x+y=3,x²+y²-3xy=4, yx^3+xy^3=_____
已知x+y=3,x²+y²-3xy=4, yx^3+xy^3=_____
x+y=3
(x+y)²=9
x²+2xy+y²=9
又已知x²+y²-3xy=4
相减,得:
5xy=5
xy=1
所以x²+y²=9-2=7
yx³+xy³
=xy(x²+y²)
=7