xy不等于0-搜答案-拍题作业网

原式=(y-x)/xy=-xy/xy=-1

移项,x=y+xy:同除y得x/y=1+x;同除X得1/y=1/x+1;移项1/x-1/y=-1

解题思路：考察命题的真假，原命题与它的逆否命题是等价命题解题过程：解：该命题的逆否命题是“若x=0，则xy=0.”是真命题原命题与它的逆否命题真假性相同所以原命题为真命题

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^2+xy-2y^2=0所以x=-2yx=y(1)x=-2y所以x/y-y/x-(x^2+y^2)/xy=-2+1/2+5/2=1(2)x=yx/y-y/x-(x^2+y^2)/xy=1-1-2

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

(1/x)-(1/y)=(y-x)/xy=-xy/xy=-1

是求x2/y2+y2/x2=吗x2-y2=xy则x/y-y/x=1两边平方得x^2/y^2-2+y^2/x^2=1所以x^2/y^2+y^2/x^2=3

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

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-

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.