三元函数求极值f(x,y,z)=200+20x+7.5y+5.5z-1.3x2-0.25y2-0.3z2+0.6xy-0

求函数Z=X2-XY+Y2-2X+Y的极值、、、步骤 x+y+z=4 xy+yz+xz=4求x2+y2+z2的解 已知x2+y2+z2-2x+4y-6z+14=0求x+y+z 已知x+y+z=a ,xy+yz+zx=b ,求x2+y2+z2 已知x2 + y2 + z2 = xy + xz + yz = 3 求x+y+z 已知x,y,z满足x/(y+z)+y/(z+x)+z/(x+y)=1,求代数式x2/(y+z)+y2/(x+z)+z2/ 已知实数x,y,z满足x/(y+z)+y/(z+x)+z/(x+y)=1,求x2/(y+z)+y2/(z+x)+z2/( 已知x+y+z=1,x2+y2+z2=2,x3+y3+z3=3,求xy(x+y)+yz(y+z)+zx(z+x)的值 已知x+y+z=1,xy+yz+zx=2,xyz2,求x2(y+z)+y2(z+x)+z2(x+y)的值 已知x+y+z=0,x2+y2+z2=1,求xy+yz+xz,x4+y4+z4的解 已知{4x-3y-3z=0,x-3y-z=0,求xy+2yz\ x2+y2-z2 已知3x-4y-z=0,2x+y-8z=0求x2+y2+z2/xy+yz+2zx的值 设x,y,z>0,且x2+y2+z2=1,试求S=xy/z+yz/x+zx/y的最小值