设根号x=a 根号下y-1=b 根号下z-2=c
x=a^2 y=b^2+1 z=c^2+2
2a+2b+2c=a^2+b^2+c^2+3
(a-1)^2+(b-1)^2+(c-1)^=0
a=1 b=1 c=1
x=1 y=2 z=3