x*1.09y*1.13=37000xy=32930

|x|/x+y/|y|+xy/|xy|=|x|/x+y/|y|+xy/|xy|=|x|/x+y/|y|+xy/|xy|=由题可知x,y都不等于0.下面分x>0,y>0x>0yx0x四种情况去绝对值,这

证明|xy|=|x||y|证明|xy|=|x||y|证明|xy|=|x||y|这个是显而易见的.（1）x,y同号xy>0|x||y|=xy=|xy|(2)x,y|x||y|=-xy=|xy|∴|xy|

xy-(x+y)=1000xy-(x+y)=1000xy-(x+y)=1000xy-x-y+1=1001(x-1)(y-1)=1001=7*11*13xy-(x+y)=1000xy-x-y=1000x

证明|xy|=|x||y|证明|xy|=|x||y|证明|xy|=|x||y|证明：（1）x,y同号时,xy>0|x||y|=xy=|xy|(2)x,y异号时,xy0|x||y|=-xy=|xy|∴|

计算：(根号xy-xy/x+根号xy)÷根号xy-y/x-y=计算：(根号xy-xy/x+根号xy)÷根号xy-y/x-y=计算：(根号xy-xy/x+根号xy)÷根号xy-y/x-y=看不懂你的题,

化简:(x+y-4xy/x+y)*(x-y-4xy/x-y)=化简:(x+y-4xy/x+y)*(x-y-4xy/x-y)=化简:(x+y-4xy/x+y)*(x-y-4xy/x-y)=题目是不是打错

y''-xy=x/y通解y''-xy=x/y通解y''-xy=x/y通解原方程化为yy''-xy^2=x即2yy''-2xy^2=2x所以(y^2)''-2xy^2=2x设p=y^2所以p''-2xp=2x那么p=

xy"=y''ln(y''/x)xy"=y''ln(y''/x)xy"=y''ln(y''/x)令z=y'',xz''=zln(z/x);令s=z/x,z=sx,x(s+xs'')=sxln(s);s+xs''=sln(

sin(xy)=x求dx/dysec(xy)-y]/x还是x/[sec(xy)-y]sin(xy)=x求dx/dysec(xy)-y]/x还是x/[sec(xy)-y]sin(xy)=x求dx/dys

（-3x^y+2xy)-()=4x^+xy（-3x^y+2xy)-()=4x^+xy（-3x^y+2xy)-()=4x^+xy(-3x^y+2xy)-(4x^+xy)=-3x^y+2xy-4x^-xy

（xy-x的平方）*x-y分之xy=（xy-x的平方）*x-y分之xy=（xy-x的平方）*x-y分之xy=您好：（xy-x的平方）*x-y分之xy=x(y-x)*xy/(x-y)=-x²y

(xy-x平方)乘以x-y份之xy=?(xy-x平方)乘以x-y份之xy=?(xy-x平方)乘以x-y份之xy=?(xy-x平方)乘以x-y份之xy=x(y-x)*xy/(x-y)=-x²y

(XY-X^2)除以X-Y/XY=?(XY-X^2)除以X-Y/XY=?(XY-X^2)除以X-Y/XY=?-X平方Y

1/x-1/y=x,求5y+xy-5y/y-xy-x=?1/x-1/y=x,求5y+xy-5y/y-xy-x=?1/x-1/y=x,求5y+xy-5y/y-xy-x=?5y+xy-5y/y-xy-x（

x*x+xy=3,xy+y*y=2,则x*x+2xy+y*y=________?x*x+xy=3,xy+y*y=2,则x*x+2xy+y*y=________?x*x+xy=3,xy+y*y=2,则x

已知XY.Y=-3,求-XY(X.X.X.Y.Y.Y.Y.Y.Y.Y-3.X.X.Y.Y.Y.Y.Y-Y)的值.（过程完整）已知XY.Y=-3,求-XY(X.X.X.Y.Y.Y.Y.Y.Y.Y-3.X

已知x+y=1,xy=-2,则x²y+xy²-2xy已知x+y=1,xy=-2,则x²y+xy²-2xy已知x+y=1,xy=-2,则x²y+xy&#

已知x-xy=8,xy-y=-9,求x+y-2xy的值已知x-xy=8,xy-y=-9,求x+y-2xy的值已知x-xy=8,xy-y=-9,求x+y-2xy的值x-xy=8(1)xy-y=-9(2)

1-2/x+y=xy,4y+6x=xy.求xy的解?1-2/x+y=xy,4y+6x=xy.求xy的解?1-2/x+y=xy,4y+6x=xy.求xy的解?1-(2/x)+y=4y+6x1-(2/x)

已知xy>0,证明xy+xy/1+x/y+y/x>=4已知xy>0,证明xy+xy/1+x/y+y/x>=4已知xy>0,证明xy+xy/1+x/y+y/x>=4xy+1/xy>=2√（xy*1/xy