已知x y=3又2分之1

1/X+1/Y=3即x+y=3xy(2x+3xy+2y)/(x-2xy+y)=(2*3xy+3xy)/(3xy-2xy)=9xy/xy=9答案为9

解1/x+1/y=5即(y+x)/xy=5∴y+x=5xy∴(2x+3xy+2y)/(x-2xy+y)=[2(x+y)+3xy]/[(x+y)-2xy]=[2×5xy+3xy]/(5xy-2xy)=(

由1/x-1/y=3得(y-x)/xy=3题中的式子分子分母同时除以xy得(2/y+3-2/x)/(1/y-2-1/x),通分得【2(x-y)/xy+3】/【(x-y)/xy-2】代入得3/5

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

(x-3xy-y)分之(2x+3xy-2y)分子分母同时除以xy得=(1/y-3-1/x)分之(2/y+3-2/x)=[-(1/x-1/y)-1]分之(-2(1/x-1/y)+3)=(-3-1)分之(

由x分之1-y分之1=2得到,1/x-1/y=2,即（y-x）/(xy)=2,即x-y=-2xy(1).2x-3xy-2y分之3x+7xy-3y=(2x-3xy-2y)/(3x+7xy-3y)(2)将

x+2的绝对值+y-3的绝对值=0所以X+2=0Y-3=0得X=-2Y=3-2又2分之1x-3分之5y+4xy=-2分之5*-2-3分之5*3+4*-2*3=5-5-24=-24

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

|x+2|+|y-3|=0所以x+2=y-3=0x=-2,y=3所以-2又2分之1x-3分之5y+4xy=5-5-24=-24

因为X+Y分之XY=2,所以XY=2(X+Y)代入后面的分子式得：13（X+Y)/5(X+Y)=13/5

(x分之1)+(y分之1)=5（x+y)/xy=5x+y=5xy代入（x+2xy+y)分之(2x-3xy+2y)=7xy分之7xy=1

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

丨x+2丨+丨y-3丨等于0所以x＋2=0,y-3=0x=-2,y=3所以负2又2分之1-3分之5y+4xy=负2又2分之1-3分之5×3+4×（-2）×3=-2.5-5-24=-31.5

x-y分之xy=-3分之1xy分之(x-y)=-3x-y=-3xyx-2xy-y分之2x+3xy-2y=(-6xy+3xy)/(-3xy-2xy)=3/5

1/x-1/y=(y-x)/xy=2y-x=2xy(3x-5xy-3y)/(-x+3xy+y)={3(x-y)-5xy}/(y-x+3xy)={(-3)*2xy-5xy}/5xy=-11/5

把要求的式子分子分母同时除以xy得(x+2xy+y)/(3x-4xy+3y)=(1/y+2+1/x)/(3/y-4+3/x)=(2+3)(3×3-4)=1

∵1/x-1/y=2∴(y-x)/(xy)=2∴y-x=2xy∴2x-3xy-2y=2(x-y)-3xy=-4xy-3xy=-7xyx-2xy-y=x-y-2xy=-2xy-2xy=-4xy∴(x-2

x分之1-y分之1=-3所以(y-x)/xy=-3y-x=-3xy从而3x-2xy-3y分之x+3xy-y=（3xy+3xy）/(3×3xy-2xy)=6/7

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

∵|x+2|+|y-3|=0两项均非负值,和为0,则均为0∴x+2=0,y-3=0∴x=-2,y=3(5y+4xy)/(-5/2*x-3)=(15-4*6)/[-5/2*(-2)-3]=-9/2=-9