已知y分之x等于3分之1则y分之x-y的值为

1/x-1/y=3得y-x=3xy∴xy=(y-x)/3则x-xy-y=x-y-(y-x)/3=4(y-x)/35x+xy-5y=5(x-y)+(y-x)/3=14(x-y)/3∴(5x+xy-5y)

1/x-1/y=2y-x=2xyx-y=-2xy(3x+7xy-3y)/(2x-3xy-2y)=[3(x-y)+7xy]/[2(x-y)-3xy]=[-6xy+7xy]/[-4xy-3xy]=xy/[

x/2=y/3=z/0.5=2zx=4z,y=6z.(x+3y-z)/(2x-y+z)=(4z+18z-z)/(8z-6z+z)=21z/3z=7.望采纳!

x/2=y/3=z/0.5=2zx=4z,y=6z.(x+3y-z)/(2x-y+z)=(4z+18z-z)/(8z-6z+z)=21z/3z=7.

x/2=y/3=z/4=tx=2ty=3tz=4tx+y-z=1/122t+3t-4t=t=1/12x=1/6y=1/4z=1/3xyz=1/6*1/4/*1/3=1/72

/>1/x-1/y=3(y-x)/(xy)=3y-x=3xyx-y=-3xy(2x-14xy-2y)/(x-2xy-y)=[2(x-y)-14xy]/[(x-y)-2xy]=[2×(-3xy)-14x

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

得xy分之y-x=3得y-x=3xy带入得-9xy-5xy分之-3xy-2xy得14分之5..求采纳.谢谢

7分之24再问：貌似错啦再答：13啊，我看成3了再答：等下再答：7分之104再问：还是错的再答：对的再答：这么简单，怎么可能错再问：不对，这是选择题再问：没这答案再答：晕，我又看错问题了再问：x，y都

1/x-1/y=(y-x)/xy=3y-x=3xy(2x-5xy-2y)/(3x-10xy-3y)=-8xy/-19xy=8/19自己算一下直接看着算的反正就是整体代入思想

x+y=1所以1/x+1/y=(1/x+1/y)(x+y)=1+y/x+x/y+1=(y/x+x/y)+2y/x>0,x/y>0所以y/x+x/y≥2√(y/x*x/y)=2所以1/x+1/y≥2+2

y分之x减y=x/y-1=3/4-1=-1/4有什么不明白可以对该题继续追问请及时选为满意答案,

在1/x+1/y=3的两边分别乘以xy,则y+x=3xy.将此代入所求的式子,有(3*3xy+xy)/(3xy-xy)=5比反了,抱歉啊!

3/4x=y/5,则x:y=4:15,y/5=z/6,则y:z=5:6,所以:x:y:z=4:15:18

x:y=2分之1:3分之1=3:2y:z=2:3,所以x:y:z=3:2:3再问：已知x:y=1.5:1，y:z=3分之2:6分之5，求x:y:z，谢谢再答：采纳我，重新问

3分之x等于5分之y则5x=3y则x=3y÷5则x÷y=3÷5所以y分之x=5分之3

x/3=y/4=z/5x：Y：Z=3；4;5

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

1/x+1/y=-1/(x+y)两边同时乘x+y得1+y/x+1+x/y=-1所以y/x+x/y=-3

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