x^2*y+xy^2=30,xy=6,求下列代数式的值（1）x^2+y^2（2）x-y

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x^2*y+xy^2=30,xy=6,求下列代数式的值（1）x^2+y^2（2）x-y

x^2*y+xy^2=30,xy=6,求下列代数式的值（1）x^2+y^2（2）x-y
x^2*y+xy^2=30,xy=6,求下列代数式的值（1）x^2+y^2（2）x-y

x^2*y+xy^2=30,xy=6,求下列代数式的值（1）x^2+y^2（2）x-y
x^2*y+xy^2=30,xy=6
xy(x+y)=30
6*(x+y)=30
x+y=5
(x+y)^2=x^2+y^2+2xy=25
x^2+y^2=25-2*6=25-12=13
x+y=5
xy=6
解得x=2,y=3,所以x-y=-1
或者x=3,y=2,x-y=1

x^2*y+x*y^2=xy(x+y)=30,又xy=6
所以x+y=5.
（1）x^2+y^2=(x+y)^2-2xy=25-12=13;
(2)因为x^2-2xy+y^2=(x-y)^2=13-12=1
所以 x-y为正负1

x^2*y+xy^2=xy(x+y)=30,
x+y=30/6=5,
x^2+y^2=(x+y)^2-2xy=25-12=13.
(x-y)^2=x^2+y^2-2xy=13-12=1,
x-y=±1

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