\left(x-a\right)^2+\left(y-a\right)^2+\left(z-a\right)^2=a^2
\left(3-a\right)^2+\left(6-a\right)^2+\left(3-a\right)^2=a^2
2\left(3-a\right)^2+\left(6-a\right)^2=a^2
2\left(9+a^2-6a\right)+36+a^2-12a=a^2
18+2a^2-12a+36+a^2-12a=a^2
18+2a^2-12a+36-12a=0
2a^2-24a+54=0
2a^2-24a=-54
​​​​​​​​​​​​​​a^2-12a=-27​​​​​​​​​​​​​​
​​​​​​​​​​​​​​​​​​​​​a\left(a-12\right)=-27​​​​​​​​​​​​​​​​​​​​​
​​​​​​​​​​​​​​​​​​​​​9\left(9-12\right)=-27​​​​​​​​​​​​​​​​​​​​​ or 3\left(3-12\right)=27

​ ​​​​​​​​​​​​​​​​​​​\left(x-3\right)^2+\left(y-3\right)^2+\left(z-3\right)^2=9

او

​​​​​​​​​​​​​​​​​​​​ \left(x-9\right)^2+\left(y-9\right)^2+\left(z-9\right)^2=81​​​​​​​