A circle is the locus of a point in a plane such that its distance from a fixed point in the plane is constant. Anologously, a sphere is the locus of a point in space such that its distance from a fixed point in space in constant. The fixed point is called the centre and the constant distance is called the radius of the circle/sphere. In anology with the equation of the circle `|z-c|=a`, the equation of a sphere of radius is `|r-c|=a`, where c is the position vector of the centre and r is the position vector of any point on the surface of the sphere. In Cartesian system, the equation of the sphere, with centre at `(-g, -f, -h)` is `x^2+y^2+z^2+2gx+2fy+2hz+c=0` and its radius is `sqrt(f^2+g^2+h^2-c)`. Q. The centre of the sphere `(x-4)(x+4)+(y-3)(y+3)+z^2=0` is

Answer

(c)