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先化简再求值2x^2y-4xy^2-2分之1xy^2 x^2y其中x=负...

解答:(每小题(3分),共6分)(1)解:原式=2xy(x+2y)∵x+2y=5,xy=1,∴2xy(x+2y)=2×1×5,=10;(2)解:∵xy=1,x+2y=5,原式=2x2y2-x2-4y2+2∴=-4x2y2-x2-4y2+2+6x2y2,=-(4x2y2+x2+4y2)+2+6x2y2,=-(x+2y)2+2+6x2y2,=-25+8,=-17.

若(x-2)的平方+|y-1|=0, 则x-2=0 x=2 y-1=0 y=1 4xy-(2x的平方+5xy-y的平方)+2(x的平方+3xy) =4xy-2x²-5xy+y²+2x²+6xy =5xy+y² =5×2×1+1 =11

[4(xy-1)^2-(xy+2)(2-xy)]÷1/4xy=[4(x^2y^2-2xy+1)+(x^2y^2-4)]÷1/4xy=(5x^2y^2-8xy)÷1/4xy=20xy-32,当x=-2,y=1/5时,原式=-8-32=-40.

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