已知x-2y=0,求分式x的平方-3xy 3y的平方的值-搜答案-智慧作业帮

x^2+y^2-6x-8y+25=0x^2-6x+9+y^2-8y+16=0(x-3)^2+(y-4)^2=0∴x=3且y=4y/x-x/y=4/3-3/4=7/12

原式＝(x^2-2x+1)+(y^2-4y+4)=(x-1)^2+(y-2)^2=0,所以x=1,y=2,代入问题得结果为3/2

此题做法不止一种,这里给你一个较简单方便的做法如果是填空题,直接把x换成4,y换成3代入即可算出正确答案

1）由1/x-1/y=5,得(y-x)/xy=5,所以y-x=5xy,即x-y=-5xy(3x+5xy-3y)/(x-3xy-y)=[3(x-y)+5xy]/[(x-y)-3xy]=(-15xy+5x

x=-2y(2xy+y^2)/(x^2-xy)=(-4y^2+y^2)/(4y^2+2y^2)=-3y^2/(6y^2)=-1/2再问：我算出来也是-1/2，可答案说是-15/28

x/2=y/3x=2y/3(3x+2y)/(2x-3y)=[3(2y/3)+2y]/[2(2y/3)-3y]=4y/(-5y/3)=-12/5

x-3y=0x=3y2x+y/x^2-2xy+y^2×(x-y)=(2x+y)/(x-y)^2*(x-y)=(2x+y)/(x-y)=(6y+y)/(3y-y)=7y/2y=7/2

x²+3分之x-2y的值为0∵x²+3>0∴x-2y=0∴x=2yx²-y²分之x²-3xy-4y²=(x-4y)(x+y)/(x+y)(x

2x=-yy=-2xxy/(x^2-y^2)=x*(-2x)/[x^2-(-2x)^2]=-2x^2/[x^2+4x^2]=-2x^2/5x^2=-2/5

x^2+y^2-6x-8y+25=（x-3)^2+(y-4)^2=0x=3,y=41/xy=1/12

因为x²+4y²-4x+4y+5=x²-4x+4+4y²+4y+1=(x-2)²+(2y+1)²=0所以得x=2,y=-1/2原式=(x&#

由1/x-1/y=2001得：y-x/xy=2001所以：xy/y-x=1/2001xy/x-y=-1/2001x-xy-y/(x-y)=x-y-xy/(x-y)=1-xy/(x-y)原式=1+1/2

(x-2y)^2=0=>x=2y=>(2x-y)/(2x+y)=(4y-y)/(4y+y)=3/5

x-5y=0,x=5y【（3x+y）/（x的2次方-2xy+y的2次方）】×（y-x）=(3x+y)/(y-x)²×(y-x)=(3x+y)/(y-x)=(15y+y)/(y-5y)=-4

x－5y=0x=5y原式=（x-y）平方/（3x+y）(y-x)=(5y-y)平方/（15y+y）(y-5y)=16y平方/-64y平方=-1/4如还有新的问题,请不要追问的形式发送,另外发问题并向我

已知x^2-xy-5y^2=0所以x(x-y)=x^2-xy=5y^2y/（x-y）-（x-y）/x=[xy-(x-y)^2/[x(x-y)]=(-x^2+xy-y^2)/(5y^2)=(-5y^2-

x^2-2x+y^2+6y+10=0(x-1)^2+(y+3)^2=0x=1y=-3(x-y)/(x+y)=4/(-2)=-2

y=4x带入3x-y=3x-4x=-xx+y=x+4x=5x(x+y)/(3x-y)=5x/(-x)=-5

∵x-y/xy=3∴x-y=3xy2x+3xy-2y/x-2xy-y=[2(x-y)+3xy]/[(x-y)-2xy]=(6xy+3xy)/(3xy-2xy)=9xy/(xy)=9