已知(x-3)=0,且xy不等于0,求x²-xy-2y²分之x²-y²的值-搜答案-智慧作业帮

3x^2－2xy－8y^2＝0,（3x+4y)(x-2y)=03x+4y=0,或,x-2y=03x=-4y,或,x=2yx/y=-4/3,或,x/y=2

(1)f(8)=f(4)+f(2)=f(2)+f(2)+f(2)=3.(2)f(x)-f(x-2)>3,f(x)>f(x-2)+f(8),f(x)>f[8(x-2)],函数在(0,+∞)是增函数,x>

x-3y=0且xy≠0,所以x=3y(x≠0,y≠0)带入分式,(9y-3y+y)/(9y+3y+y)=7/13

x-3y=0x=3yx*2-xy+y*2/x*2+xy+y*2=(9y^2-3y^2+y^2)/(9y^2+3y^2+y^2)=7y^2/13y^2=7/13

3x²-2xy-8y²=0两边同除y²得:3(x/y)²-2(x/y)-8=0(3x/y+4)(x/y-2)=0x/y=2或x/y=-4/3

由x+y-3xy+5=0得x+y+5=3xy．∴2xy+5≤x+y+5=3xy．∴3xy-2xy-5≥0，∴（xy+1）（3xy-5）≥0，∴xy≥53，即xy≥259，等号成立的条件是x=y．此时x

因为xy不为0,所以3x^2-2xy-8y^2=0可以两边同时除以y^2,得3(x/y)^2-2(x/y)-8=0即(3x/y+4)(x/y-2)=0解得x/y=2或者x/y=-4/3希望有用.

3x²-2xy-8y²=0(x-2y)(3x+4y)=0x=2y或3x=-4yx/y=2或x/y=-4/3

xy≠0,所以x≠0,y≠03x²-2xy-8y²=0两边除于xy3（x/y）-2-8（y/x）=0设x/y=t;t≠03t-8/t-2=03t²-2t-8=0(t-2)

一因为f(xy)＝f（x）＋f（y）f(8)=f(2.4)=f(2)+f(4)而f(4)=f(2.2)=f(2)+f(2)所以f(8)=3.f(2),而f(2)=1所以f（8）=3二f（x）－f（x－

填：3x+2y-2xy=02y+3x=2xy(2y+3x)/(2xy)=1(1/x)+(3/y)=1根据均值不等式得1≥2√(3/(xy))1≥12/(xy)xy≥12所以xy的最小值是12

(1)要使得函数f(x)有意义,则：ax-1＞0；即：ax＞1当0＜a＜1时,函数f(x)的定义域为：(-∞,0).当a＞1时,函数f(x)的定义域为：(0,+∞).（2）当0＜a＜1时,函数f(x)

2分之1或负4分之3

无解

已知|X|=3,|Y|=2,且XY

B因为XY

1.x=1,y=1,√xy+y分之x+√xy=12.将△DFC绕点D顺时针旋转180°,得到△DGB,连接EG.则△DFC≌△DGB.所以FD=DG,BG=FC,角FDC=角BDG有因为DE.DF分别

因为,x-y=3xy所以：-3x+6xy+3y/[(7x-5y)-9xy-(3x-y)]=[-3(x-y)+6xy]/[(7x-5y)-9xy-(3x-y)]=[-3*3xy+6xy]/[7x-5y-

设t=xy则：x=t/yxy=x+y+3t=t/y+y+3y^2+(3-t)y+t=0△=(3-t)^2-4t=9-10t+t^2=(t-1)(t-9)≥0t≥9,或,t≤1因为x,y大于0,所以,y

2X^2+3xy-2y^2=0(2x-y)(x+2y)=0即：2x-y=0或,x+2y=0y=2x或x=-2y当y=2x时：x+y/x-y=3x/(-x)=-3当x=-2y时：x+y/x-y=-y/(

∵x-y=4xy∴原式=[2(x-y)+3xy]/[-(x-y)-2xy]=(8xy+3xy)/(-4xy-2xy)=11xy/(-6xy)=-11/6