已知x-3y=0,求分式

代入方法：分母：3x-3xy+3y=3(x+y)-3xy=3•(3xy)-3xy=9xy-3xy=6xy分子：x+xy+y=x+y+xy=3xy+xy=4xy所以原式=6xy/4xy=3/

(x+y-z)/z=(y+z-x)/x=(z+x-y)/y[x+y]/z-1=[y+z]/x-1=[z+x]/y-1[x+y]/z=[y+z]/x=[z+x]/y设[x+y]/z=[y+z]/x=[z

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

2x-3y=0所以y=2x/3代入(x^2+xy-y^2)/(2x^2+xy-y^2)得到[x^2+x*2x/3-(2x/3)^2]/[2x^2+x*2x/3-(2x/3)^2]=(x^2+2x^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

原式=(2x+y)/(x-y)x-3y=0所以x=3y代入得原式=(6y+y)/(3y-y)=7y/2y=7/2

由1/x-1/y=3两边同乘以xy得y-x=3xy即x-y=-3xy所以(3x+3xy-3y)/(x-2xy-y)＝3(x-y+xy)/(x-y-2xy)=3(-3xy+xy)/(-3xy-2xy)=

y²-3y+1=0两边除以y得y-3+1/y=0y+1/y=3两边平方得y²+2+1/y²=9∴y²+1/y²=7y²+1+1/y²

这一题要先将待求式化简原式分母=X^4-Y^4=(X^2-Y^2)(X^2+Y^2)=(X-Y)(X+Y)(X^2+Y^2)分子分母约去(X+Y)(X^2+Y^2),则原式可化简为1/(X-Y),带入

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

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

3X-4y=03x=4yx:y=4:3x=4ay=3a3x²-y²分之x²＋2xy=(16a^2+2x4ax3a)/(3x16a^2-9a^2)=40a^2/39a^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

3x+2y=0y=-1.5xx/y=x/-1.5x=-2/3y分之3x+3=3x/-1.5x+3=1