Question

x*x+y*y+2z*z-2x+4y+4z+7=0,求xyz的值

Answer 1

x*x+y*y+2z*z-2x+4y+4z+7=0

(x*x-2x+1)+(y*y+4y+4)+2(z*z+2z+1)=0

(x-1)^2+(y+2)^2+2(z+1)^2=0

x=1,y=-2,z=-1

xyz=2