已知X Y分之XY=A X Z分之XZ=B Y Z分之YZ=C 且ABC

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

1、答案：负七分之五解题：xy=2x+2y代入原式,整理合并同类项即可得出2、如果只考虑在同一平面内,有三条线.如图

-5分之2

x/y=3x=3y(x²+2xy-3y²)/(x²-xy+y²)=(9y²+6y²-3y²)/(9y²-3y²

1）若x,y同为正数,则x分之|x|+y分之|y|+xy分之|xy|=1+1+1=32）若x,y同为负数,则x分之|x|+y分之|y|+xy分之|xy|=-1-1+1=-13）若x,y异号,比如x为正

xy分之x+y=3所以1/x+1/y=3(2x-3xy+2y)/(-x+2xy-y)分子分母同除以xy=[2(1/x+1/y)-3]/[-(1/x+1/y)+2]=(6-3)/(-3+2)=-3

∵(x+y)分之xy=3∴xy=3(x+y)∴(-2x+3xy-2y)分之(3x-5xy+3y)=[-2(x+y)+9(x+y)]分之[3(x+y)-15(x+y)]=[7(x+y)]分之[-12(x

因为x-y=4xy所以x-2xy-y=2xy2x+3xy-2y=11xyx-2xy-y分之2x+3xy-2y=5.5

x+y分之xy=3,xy/(x+y)=3,xy=3(x+y)-x+3xy-y分之2x-3xy+2y=(2x-3xy+2y)/(-x+3xy-y)=[2x-9(x+y)+2y]/[-x+9(x+y)-y

1/x+1/y=-2则(x-xy+y)/(x+xy+y)分子分母同除以xy=(1/x+1/y-1)/(1/x+1/y+1)=(-2-1)/(-2+1)=3

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

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+y分之xy=2,则xy/(x+y)=2xy=2x+2y(-x+3xy-y)分之(3x-5xy+3y)=(3x-5xy+3y)/(-x+3xy-y)=[3x-5(2x+2y)+3y)/[-x+3(2

(y-x)/xy=3y/xy-x/xy=3所以1/x-1/y=3(3x-5xy-3y)/(x-2xy-y)分子分母同时除以xy原式=(3/y-5-3/x)/(1/y-2-1/x)=[3(1/y-1/x

(3x^2+2xy)/xy-(2x^2-xy)/xy=(3x^2+2xy-2x^2+xy)/xy=(x^2+3xy)/xy=x(x+3y)/xy=(x+3y)/y

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

x+y分之xy=2,则xy/(x+y)=2xy=2x+2y(-x+3xy-y)分之(3x-5xy+3y)=(3x-5xy+3y)/(-x+3xy-y)=[3x-5(2x+2y)+3y)/[-x+3(2

设x+y=axy=b,则b/a=3b=3a所以-X+3XY-Y分之2X-3XY+2Y可以写成(2a-3b)/(3b-a)=-7/8

x/3-y/4=3x+2y==>4x-3y=36x+24y==>①32x=-27y==>x=-27y/32②(4x-3y)^2=(36x+24y)^2②==>16x^2+9y^2-24xy=1296x

∵x-y=4xy∴原式=[2(x-y)+3xy]/[-(x-y)-2xy]=(8xy+3xy)/(-4xy-2xy)=11xy/(-6xy)=-11/6