3x-6y=0求XY

x/2=y/3x=2y/3所以x²-2xy-3y²/x²-6xy-7y²=(x+y)(x-3y)/(x+y)(x-7y)=(x-3y)/(x-7y)=(2y/3

x²-5xy+6y²=0(x-2y)(x-3y)=0x=2y,x=3y所以x/y=2,x/y=3

移项得x^2-5xy+6y^2=0由于y不等于=两边同除以y^2则有(x/y)^2-5(x/y)+6=0分解因式：（x/y-2)(x/y-3)=0则有x/y=2或x/y=3

3x*+xy-2y*=0（3x-2y）(x+y)=0那么x=2y/3或x=-yy/x=3/2或x/y=-1(x/y)-(y/x)-(x*+y*)/(xy)=(x/y)-(y/x)-(x/y+y/x)=

绝对值大于等于0,相加等于0,若有一个大于0,则另一个小于0,不成立所以两个都等于0所以x+y+1=0xy+3=0xy=-3x+y=-1两边平方x^2+2xy+y^2=(-1)^2x^2+y^2=1-

因为x/y=2所以x=2y是[x^2-xy+3y^2]/[x^2+xy+6y^2]吧=(4y^2-2y^2+3y^2)/(4y^2+2y^2+6y^2)=5y^2/12y^2=5/12

y-x-2xy=0y-x=2xyx-y=-2xy(3x+xy-3y)/(y-xy-x)=[3(x-y)+xy]/[(y-x)-xy]=(-6xy+xy)/(2xy-xy)=-5xy/xy=-5

x^+2xy+y^+4=16(x+y)²=16-4=12(1)x^-2xy+y^=16(x-y)²=16(2)(1)-(2)2y*2x=-4xy=-1(3xy+6y^)+|x^-(

(X-3Y)(X-2Y)=01）X=3Y（X^2+3XY)/2Y^2=(9Y^2+9Y^2)/2Y^2=92)X=2Y原式=(4Y^2+6Y^2)/2Y^2=5

∵x-y=6,xy=4∴(x-y)²=36∴x²-2xy+y²=36∴x²+y²=36+2×4=44两边除以xyx/y+y/x=44/4=11∴xy^

因为x^2-5xy+6y^2=0,所以(x-2y)(x-3y)=0,所以x-2y=0或x-3y=0,所以x=2y或x=3y,当x=2y时,(x^2+3xy)/(2y^2)=(4y^2+6y^2)/(4

[(2x+6)/(x^2-2xy+y^2)]*(x-y)是不是给错了,应该是[(2x+6y)/(x^2-2xy+y^2)]*(x-y)吧?x-3y=0得x=3y代入[(2x+6y)/(x^2-2xy+

x=-1y=2代入求值就可以

（x+y)（x-y)-y^2+（x-y)^2-（6x^2y-2xy^2)÷2y=（x+y)（x-y)-y^2+（x-y)^2-2y（3x^2-xy)÷2y=（x+y)（x-y)-y^2+（x-y)^2

y-x-2xy=0所以x-y=-2xyy-x=2xy所以原式=[3(x-y)+xy]\[(y-x)-xy]=[3×(-2xy)+xy]\(2xy-xy)=-5xy\xy=-5

-2x+6xy-2y/(7x+5y)-9xy-(3x+y)=[3(x+y)-x-y]/[7x+5y-9/2(x+y)-3x-y]=2(x+y)/[-1/2(x+y)]=-4

xy/x+y=6∴xy=6(x+y)3x-2xy+3y/-x+3xy-y=[3x-12(x+y)+3y]/[-x+18(x+y)-y]=-9(x+y)/17(x+y)=-9/17再问：你在啊？再答：在

已知x+xy=-2,xy-y=-6则X+Y=42x｛-4y-3[（x+xy）²+x]-½[（y-xy）²-2y]=2x｛-4y-3[（-2）²+x]-&fr

不会

x+y=5xy（2x-3xy+2y)/(x+2xy+y）=[2（x+y）-3xy]/[(x+y)+2xy]=(2×5xy-3xy)/(5xy+2xy)=7xy/7xy=1再问：若x＋1/x＝3,求(x