Step 1:

The equation of the sphere is .

Rewrite the expression.

Take out 2 as a common factor.

Divide each side by 2.

Group the terms.

Complete the each squares.

Compare this equation with .

So this equation represents the equation of the sphere.

Where is the center of the sphere.

r is the radius of the sphere.

From above, and .

Solution :

The center of the sphere is .

The radius of the sphere is .