x^3-3xy^2+i(3xy^2-y^3)如何变成z^3

x^3+y^3+z^3-3xyz变成(x+y+z)(x^2+y^2+z^2-xy-yz-xz)步骤 5xy^2-[3xy^2-(4xy^2-2x^y)]+x^2y-xy^2如何化简 证明 (x+y+z)^2>3(xy+yz+zx) 5yz/(y+z)=6,4xy/(z+x)=3,3xy/x+y=2 已知X:Y:Z等于3:4:5,求2XY-3XY+Z的平方除以X平方减2XY减Z平方 实数x、y、z满足x=6-3yx+3y-2xy+2z (x-2xy)*(-xy+2y*y)-(3x*x-2xy)(x-9xy+6y*y) 已知三个数x,y,z,满足xy/x+y=-2，yz/y+z=4/3,zx/z+x=-4/3,求(xyz)/(xy+yz+ x²-2xy+y²分之x²+2xy-3y³如何因式分解 求I=∫∫ xz^2dydz+(y*x^2-z^3)dzdx+(2xy+z*y^2)dxdy /x^2+y^2+z^2, -2x²y（3xy²z-2y²z) -2x²y(3xy²z-2y平方z)