已知x-y=1,xy=3求x的3次方乘以y-2x²y² xy的3次方的值,并解析

1/x+1/y=3∴x+y=3xy3x-2xy+3y/x+xy+y=[3(x+y)-2xy]/[(x+y)+xy]=(9xy-2xy)/(3xy+xy)=7/4

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/

已知1/x-1/y=3,应该是1/x+1/y=3,[按原式得不出结果!]如此,则3xy＝x+y（3x-xy+3y）/（x+xy+y）＝2

=-x-(2y-2+3x)+2(x+4)=-x-2y+2-3x+2x+8=-4x-2y+10

首先化简通分1/x+1/y=5得：（x+y)/xy=5即有x+y=5xy将要求的分式化简：3x+xy+3y/x-2xy+y=3x+3y+xy/x+y-2xy（根据加法交换律）=3（x+y)+xy/(x

因为1/x+1/y=3所以x+y=3xy所以x+xy+y/2x-3xy+2y=（3xy+xy)/(6xy-3xy)=4xy/3xy=4/3

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(x+2xy+y)/(2x-3xy+2y)=

(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)=-6xy+3x-3y=-6×(-2)+3×1=15

1/x-1/y=3(Y-X)/XY=3Y-X=3XYX-Y=-3XY(x-2xy-y)/(5x+3xy-5y)=(-3XY-2XY)/(-15XY+3XY)=-5XY/-12XY=5/12

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-2x

1/x+1/y=(x+y)/xy=8x+y=8xy2x-3xy+2y/x+2xy+y=[2(x+y)-3xy]/[(x+y)+2xy]=(16xy-3xy)/(8xy+2xy)=13xy/10xy=1

是求(3x+xy+3y)/(x-xy+y)吧?(3x+xy+3y)/(x-xy+y)上下同除以xy=(3/y+1+3/x）/(1/y-1+1/x)=[3(1/x+1/y)+1]/(1/x+1/y-1)

(x+xy+y)/(2x-3xy+2y)的上下各项均除以xy得(1/y+1+1/x)/(2/y-3+2/x)=(1+3)/(6-3)=4/3☆⌒_⌒☆希望可以帮到you~

设1/x-1/y=t(5x+xy-5y)/(x-xy-y)=(1-5(1/x-1/y))/(-1-(1/x-1/y))=(5t-1)/(t+1)至于是1/x-1/y=3还是1/y-1/x=3都差不多

分子,分母同时除xy(3/y-5-3/x)/(-1/y+3+1/x)=(6-5)/(3-2)=1

1/x-1/y通分=(y-x)/xy=3y-x=3xyx-y=-3xy所以原式=[3(x-y)+4xy]/[(x-y)-2xy]=[3(-3xy)+4xy]/[(-3xy)-2xy]=-5xy/(-5

已知条件不对吧?再问：已经改正了！再答：请你把题目检查一遍谢谢再问：我把错误的地方改在补充问题里了……再答：步骤如下1/X-1/Y=3等式两边同乘以XY得到Y-X=3XY原试=（3X+XY-3Y）/（

1/x+1/y=5(x+y)/xy=5x+y=5xy(3x-5xy+3y)/(x+xy+y)=(15xy-5xy)/(5xy+xy)=10/6=5/3

同除xy原式变形为：（3/y-4+3/x）/(1/x+2+1/y)=5/5=1

(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)=-2xy+2x+3y-3xy-2y+2x-x-4y-xy=-6xy+3x-3y=-6*(-2)+3*1=15不懂可追问,有帮助请采