已知y分之x=2,则y分之x y=

3/x-2/y=3等式两边同乘以xy3y-2x=3xy(2x-3y-xy)/(7xy+9y-6x)=[-(3y-2x)-xy]/[3(3y-2x)+7xy]=(-3xy-xy)/[3·(3xy)+7x

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

3x²+xy-2y²=0(x+y)(3x-2y)=0x=-y,或3x=2yy/x=-1,或3/2x/y-y/x-(x²+y²)/(xy)=x/y-y/x-x/y

(x-y)/(x+y)=(x-y)(x+y)/[(x+y)^2]=(x^2-y^2)/[x^2+y^2+2xy]=2xy/[x^2+y^2+x^2-y^2]=2xy/(2x^2)=y/xx^2-y^2

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

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

(5x+3xy-5y)/(x-2xy-y)=(5/y+3-5/x)/(1/y-2-1/x)分子分母同时除以xy=[-5(1/x-1/y)+3]/[-(1/x-1/y)-2]=(-15+3)/(-3-2

1/x-1/y=(y-x)/xy=3y-x=3xy所以x-y=-3xy所以原式=[(x-y)-2xy]分之[2(x-y)-5xy]=[(-3xy)-2xy]分之[2(-3xy)-5xy]=(-5xy)

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

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

xy/(x+y)=2(x+y)/xy=1/21/x+1/y=1/2(3x-xy+3y)/(-x+3xy-y)=(3/y-1+3/x)/(-1/y+3-1/x)=[3(1/x+1/y)-1]/[(3-(

1/x+1/y=5(x+y)/x*y=5x+y=5*x*yx+2xy+y=x+y+2xy=5xy+2xy=7xy2x-3xy+2y=10xy-3xy=7xy(2x-3xy+2y)/(x+2xy+y)=

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

y=(x²-3xy-2y²)/2y2y²=x²-3xy-2y²x²-3xy-4y²=0(x-4y)(x+y)=0x=4y或x=-y

xy分之【x加y】等于2分之一xy=2(x+y)【xy加x加y】分之xy=2(x+y)/[2(x+y)+x+y]=2(x+y)/[3(x+y)]=2/3

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+y)/(x-y)=3/2[(x/y)+1]/[(x/y)-1]=3/23(x/y)-3=2(x/y)+2x/y=5y/x=1/5(x^2+y^2)/xy=x/y+y/x=5+1/5=26/5

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