作业帮x+y=-5,xy=3,则-x^3y-xy^3+2x^2y^2等于
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x+y=-5,xy=3,则-x^3y-xy^3+2x^2y^2等于
x+y=-5,xy=3,则-x^3y-xy^3+2x^2y^2等于
x+y=-5,xy=3,则-x^3y-xy^3+2x^2y^2等于
原式可化简为
xy(-x^2-y^2+2xy)
=xy(-x^2-y^2-2xy+4xy)
=xy(-(x+y)^2+4xy)
注：-x^2-y^2-2xy=-（x+y）
将1,2式代入得,
3*（-（-5）^2+4*3)
=-39
-x^3y-xy^3+2x^2y^2
=-xy(x²+y²-2xy)
=-xy(x²+y²+2xy-4xy)
=-xy[(x+y)²-4xy]
=-3×[(-5)²-4×3]
=-3×13
=-39
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