如果2x y=0,xy不等于0,那么分子式-搜答案-搜搜考试网

如果xy>0,xz、

当x>0时,y>0,z

x+2y=0x=-2y2xy+y2/x2-xy=-4y^2+y^2/4y^2+2y^2=-5/6

f(x,y)={xy/[2-√(4+xy)]=-2-√（4+xy),xy≠0；{4,xy=0,在点(0,0),(1,0)处不连续,在（1,2）处连续.再问：能简述下原因么？再答：f(0+,0+)=-4

3x2-2xy-8y2=(3x+4y)(x-2y)=0so3x+4y=0orx-2y=0x/y=-4/3or2

x+2y=0x=-2y2xy+y2/x2-xy=-4y^2+y^2/4y^2+2y^2=-5/6

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.

令X/Y=T因为XY不等于0将3x^2-2xy-8y^2=0同除XY则得3X/Y-2-8Y/X=0将T代入得3T-2-8/T=0--------（1）因为XY不等于0则X不等于0Y不等于0X/Y也不等

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

因为x+2y=0,所以x=-2y原式=(x^2+2xy)/(xy+y^2)=(4y^2-4Y^2)/(-3y^2+y^2)=0/(-2y^2)又因为xy不等于零,所以x、y君不等于零,所以-2y^2亦

3x²+3xy=03x²=-3xy因为x不等于0所以x=-y所以x：y=1：-1

xy不等于0所以x≠0,y≠03x^2-2xy-8y^2=0两边除以y^2=>3(x/y)^2-2(x/y)-8=0=>[(x/y)-2][3(x/y)+4]=0=>x/y=2,或x/y=-4/3

x+2y=0,xy不等于0∴x=-2yx²+2xy/xy+y²=(4y²-4y²)/(-2y²+y²)=0

3x+4y=0,即x=-4y/32xy+y²/x²-xy=2y(-4y/3)+y²/(-4y/3)²-(-4y/3)y=(-5/3)y²/(28/9)

3x²-2xy-8y²=0(3x+4y)(x-2y)=03x=-4y,x=2y所以x/y=-4/3或2

2分之1或负4分之3

2x²-xy-2y²=0两边同除以x²得：2-(y/x)-2(y/x)²=0(y/x)²+1/2(y/x)=1(y/x+1/4)²=1+1/

2x2+5xy-3y2=0(2X-Y)(X+3Y)=0==>X=Y或者X=-3YXY不等于0,即X,Y都不等于0所以X:Y=X/Y=1或者-1/3

无解

x^2+xy-6y^2=0化简得（x-2y)(x+3y)=0x=2y或x=-3y分别带入2x^2-3xy+y^2/5x^2-7xy+2y^2化简即可.