X+Y=2500 Z=2X/5+XY/10000 求Z的最大值 X..Y分别为多少?其中X>600 Y>300 X Y取整数

X-5分之1X=Z,Y-2分之1Y=Z,2Z+9=XY 已知XY=2(X+Y),YZ=4(Y+Z),ZX=5(Z+X),求X,Y,Z已知XY=2(X+Y),YZ=4(Y+Z),ZX=5(Z+X),求X,Y,Z 已知1/x=5/y+z=3/z+x 求2xy/yz ÷x/Y的值 方程组xy/x+y=2 yz/y+z=4 zx/x+z=5 求x,y,z 若|x-3|+|y+2|+|2z+1|=0,求(xy-yz)(y-x+z) X-y-z=x+( )=x-( ) 1-x+2xy-y=1-( ) 已知x+y+yz=5,y+z+xy=8,x+z+xy=9,求x,y,z 已知x,y,z∈R,求证:x^2+y^2>=xy+x+y-1 解方程组：x+y=2 ,xy+z=1 xy+yz+zx=1,x,y,z>=0求证 1/(x+y)+1/(y+z)+1/(x+z)>=5/2abc=1 xy+x+y=1,yz+z+y=5,zx+z+x=2,求x y z的值 解方程组：xy+x+y=1 yz+y+z=5 zx+z+x=2 已知z=x^2+5/4y^2-xy-x-1/2y+1,则z的最小值是 已知z=x^2+5/4y^2-xy-x-1/2y+1,则z的最小值是 (x+y-xy)/(x+y+2xy)=(y+z-2yz)/(y+z+3yz)=(z+x-3zx)/(z+x+4zx),且2/x=3/y=1/z,则xyz=? 已知（x+y-xy）/(x+y+2xy)=(y+z-2yz)/(y+z+3yz)=(z+x-3zx)/(z+x+4zx),且2/x=3/y-1/z,则xyz=? 设z=f(x^2-y^2,e^（xy)),求偏导z/x,偏导z/y 已知XY+X/X+Y+1=2 XZ+2X/X+Z+2=3 (Y+1)(Z+2)/Y+Z+3=4 求X+Y+Z的值已知(XY+X)/(X+Y+1)=2 (XZ+2X)/(X+Z+2)=3 [(Y+1)(Z+2)]/(Y+Z+3)=4 求X+Y+Z的值