2.若x3+y3=1000,x2y-xy2=-498,则(x3-y3)+(4xy2-2x2y)-2(xy2-y3)= 。

2.若x3+y3=1000,x2y-xy2=-498,则(x3-y3)+(4xy2-2x2y)-2(xy2-y3)= ----

X3-Y3+4XY2-2X2Y-2XY2+2Y3
=X“3”+Y“3”+2XY“2”-2X“2”Y
=1000-2×498=4
打了引号的是立方和平方
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第1个回答  2006-01-16
好变态的题…………

(x3-y3)dx+xy2dy
应该是x3+y3=1000,x2y-xy2=-496(x3-y3)+(4xy2-2x2y)-2(xy2-y3)=x^3-y^3+4xy^2-2x^2y-2xy^2+2y^3=x^3+y^3+2xy^2-2x^2y=(x^3+y^3)-2(x^2y-x^2y)=1000+2×496=1992

x+y=10,x3+y3=100,则x2+y2=?
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