Concept:
The general equation of a sphere is
\[
x^2+y^2+z^2+2ux+2vy+2wz+d=0
\]
Its centre is
\[
(-u,-v,-w)
\]
Step 1: Use the given points.
The sphere passes through
\[
(1,0,0)
\]
Substitute in the general equation:
\[
1+2u+d=0
\]
So,
\[
2u+d=-1
\]
It passes through
\[
(0,1,0)
\]
So,
\[
1+2v+d=0
\]
\[
2v+d=-1
\]
It passes through
\[
(0,0,1)
\]
So,
\[
1+2w+d=0
\]
\[
2w+d=-1
\]
Step 2: Compare the equations.
\[
2u+d=2v+d=2w+d
\]
Therefore,
\[
u=v=w
\]
Let
\[
u=v=w
\]
Then centre is
\[
(-u,-u,-u)
\]
Step 3: Use centre condition.
The centre lies on
\[
x+y+z=6
\]
So,
\[
(-u)+(-u)+(-u)=6
\]
\[
-3u=6
\]
\[
u=-2
\]
Thus,
\[
v=-2,\quad w=-2
\]
Step 4: Find \(d\).
Use
\[
1+2u+d=0
\]
Substitute \(u=-2\):
\[
1+2(-2)+d=0
\]
\[
1-4+d=0
\]
\[
d=3
\]
Step 5: Write the sphere equation.
\[
x^2+y^2+z^2+2ux+2vy+2wz+d=0
\]
\[
x^2+y^2+z^2+2(-2)x+2(-2)y+2(-2)z+3=0
\]
\[
x^2+y^2+z^2-4x-4y-4z+3=0
\]
Step 6: Final answer.
\[
\boxed{x^2+y^2+z^2-4x-4y-4z+3=0}
\]