{7分之-x-6分之x y=2分之1 5(x y)-2(y-x)=1

原式=（2x+y）/（5xy-6xy）×（1/2）（x+2y）=（x+y）/（-xy）×（1/2）（x+y）=（-xy）/（2x+2y）=（-xy）/2(x+y)=（1/2）×（-xy）/(x+y)当

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

(1+4/5)x=9/16x=5/16(1-7/15)x=14/25x=21/10(1+3/4)x=5/6x=10/21

1/x-1/y=2(y-x)/xy=2y-x=2xy所以x-y=-2xy原式=[2(x-y)+7xy]分之[(y-x)+xy]=[2(-2xy)+7xy]分之[(2xy)+xy]=3xy]分之3xy=

x/y=7/2(x²-3xy+2y²)/(x²+2xy+y²)=[(x/y)²-3(x/y)+2]/[(x/y)²+2(x/y)+1]=[(

∵y/x=3∴y=3x∴原式=(3x²-12x²+18x²)/（6x²-3x*3x+7*9x²)=9x²/(60x²)=3/20

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

再答：满意请采纳，谢谢了

已知分式4x^2-1分之6x^2+x-2的值为0,则x^-1=∵分式4x^2-1分之6x^2+x-2的值为0∴6x²+x-2=04x²-1≠0(3x+2)(2x-1)=0∴3x+2

xy/(x+y)=51/x+1/y=1/5yz/(y+z)=7/21/y+1/z=2/7zx/(z+x)=41/x+1/z=1/4(xy+yz+zx)分之xyz=1/(1/x+1/y+1/z)=280

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

您好：X－4分之3=6分之5x=5/6+3/4x=10/12+9/12x=19/122分之1+X=3分之23/2x=2/3x=2/3÷3/2x=4/9X+4分之3=8分之7x=7/8-3/4x=7/8

∵x/y=2/3∴设x=2t,y=3t∴(x²+3xy)/(x²+xy-6y²)=(4t²+3×2t×3t)/(4t²+2t×3t-6×9t²

原式=xy分之(x²-y²)+x(x-y)分之y(x-y)=xy分之(x²-y²)+x分之y=xy分之(x²-y²+y²)=xy分

(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

由已知条件可得：x-y=-4xy,（也就是在等式两边乘xy后整理,即可）,代入所求的式子里分母为-4xy+7xy,即3xy；分子为-4xy-2xy,即-6xy,化简得-2

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=5两边乘xyy-x=5xyx-y=-5xy所以原式=[6(x-y)+7xy]/[-8(x-y)-9xy]=[6(-5xy)+7xy]/[-8(-5xy)-9xy]=-23xy/(31x