已知2x y=5,则y-搜答案-百度作业网

xy/x+y=3则xy=3(x+y)2x-5xy+2y/x-3xy+y=2(x+y)-5xy/(x+y)-3xy=2(x+y)-15(x+y)/(x+y)-9(x+y)=-13(x+y)/-8(x+y

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(3x-4y+5xy)-(2x-3y)+5xy=3x-2x-4y+3y+5xy+5xy=x-y+10xy=3+4×10=43

（3x-4y+5xy）-（2x-3y）+5xy=3x-4y+5xy-2x+3y+5xy=(x-y)+10xy=3+50=53

（3x-4y+2xy）-（2x-5y+5xy）=x+y-5xy=10

-xy（x^2y^5-xy^3-y)=-(xy^2)^3+(xy^2)^2+xy^2=-(-2)^3+4-2=8+4-2=10

x^2y+xy^2=xy(x+y)=1/5

xy/(x+y)=2∴xy=2(x+y)(3xy-x-y)/(3x-5xy+3y)=[6(x+y)-x-y]/[3x+3y-10(x+y)]=5(x+y)/[-7(x+y)]=-5/7

x²y+xy²=xy(x+y)=10

x^2y+xy^2=xy(x+y)=(-3)×5=-15

x+y=5,xy=-3,则x^2y+xy^2=xy(x+y)=-3*5=-15

(5x-xy+5y)/(3xy-x-y)=[5(x+y)-xy]/[3xy-(x+y)]=[5(x+y)-2(x+y)]/[6(x+y)-(x+y)]=1/2

(3x-4y+5xy)-(2x-3y-2xy)=3x-4y+5xy-2x+3y+2xy=x-y+7xy=4+7×(-2)=4-14=-10

∵x-y=4xy，∴2x+3xy-2yx-2xy-y=2(x-y)+3xyx-y-2xy=8xy+3xy4xy-2xy=112．故答案为：112．

因为xy/（x+y）=1/2所以x+y=2xy原式=3（x+y)-5xy/(-x-y+3xy)=3*2xy-5xy/(-2xy+3xy)=xy/xy=1

yx+xy=x2+y2xy=(x+y)2-2xyxy当x+y=2，xy=-5时，原式=22-2×(-5)-5=-145．故答案为-145．

xy/(x+y)=2xy=2(x+y)(3x-5xy+3y)/(-x+2xy-y)=[3(x+y)-5xy]/[2xy-(x+y)]=[3(x+y)-10(x+y)]/[4(x+y)-(x+y)]=-

（3x-4y+5xy）-（2x-3y）+5xy=3x-4y+5xy-2x+3y+5xy=x-y+10xy=3+10*5=53

原式=-xy²（x²y^4-xy²-1）∵xy²=-2原式=2（（-2)²-（-2）-1）=10