x平方-2x 2y-xy
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(x+y)(xy)=x^2y+xy^2=-8原式=-7
解2(x²-xy)-3(2x²-3xy)=(2x²-6x²)+(-2xy+9xy)=-4x²+7xy再问:����|-15|-8�£�-2��+4*�
xy+x2=xy2+xy2+x2≥33x4y24=3当且仅当xy2=x2时成立所以xy+x2的最小值为3故选A.
[2x(x2y-xy2)+xy(xy-x2)]÷x2y=[2x3y-2x2y2+x2y2-x3y]÷x2y=x-y,把x=2013,y=2012代入上式得:原式=x-y=2013-2012=1.
原式=2x2y+2xy-3x2y-3xy-4x2y=-5x2y-xy当x=-2,y=12时,原式=-9.
原式=4x2y-6xy+3(4xy-2)+x2y+1=5x2y+6xy-5当x=2,y=-12时,原式=5×4×(-12)+6×2×(-12)-5=-21.
∵xy+x+y+7=0  
解-x²y-xy²=-xy(x+y)=-2×5=-10
3xy(x²y-xy²+xy)-xy²(2x²-3xy+2x)=3x³y²-3x²y³+3x²y²-
∵2x+y=4,xy=3,∴2x2y+xy2=xy(2x+y)=3×4=12.故答案为:12
x=2013,y=2013[3x(x²y-xy²)+xy×(3xy-2x²)]/(x²y)=[3x²y(x-y)+x²y×(3y-2x)]/
2x²-3xy+(2xy-x²)=2x²-3xy+2xy-x²=x²-xy=x(x-y)
(x+y)(x-y)-y^2+(x-y)^2-(6x^2y-2xy^2)/(2y)=X^2-y^2-y^2+X^2+y^2-2xy-3x^2+xy=-x^2-y^2-xy=-(x^2+y^2+xy-3
x2y+xy2=xy*(x+y)因为x+y=-(7+xy)又x+y=(9+2xy)\3所以(9+2xy)\3=-(7+xy)3+2xy\3=-7-xy5xy\3=-10解得xy=-6所以x+y=-(7
由题意得(x-2)平方+(y-2)平方+(x-y)平方=0,故x=y=2,故x平方y=8
原式=2x2y+2xy-3x2y+3xy-4x2y=-5x2y+5xy,当x=-1,y=1时,原式=-5×(-1)2×1+5×(-1)×1=-5-5=-10.
原式=-xy(x-y),当x-y=3,xy=-2时,则原式=-3×(-2)=6.故答案为:6.
解3xy²-[2xy²-2(xy-1.5x²y)]+xy-3x²y=3xy²-(2xy²-2xy+3x²y)+xy-3x²
∵x2-y2=xy,∴原式=x2y2+y2x2=x4+y4x2y2=(x2−y2)2+2x2y2x2y2=3x2y2x2y2=3.再问:先化简2a+1/a²-1÷a²-a/a
∵x+2y=5,xy=1,∴2x2y+4xy2=2xy(x+2y)=2×1×5=10,故答案为:10.