VITEEE 2010 Paper

The equation of sphere concentric with the sphere x2+y2+z2−4x−6y−8z−5=0 is
x2+y2+z2−4x−6y−8z+c=0 ...(i)
Since, this sphere eq.(i) passes through origin, therefore
0+0+0−0−0−0+c=0
⇒ c = 0
Hence, the required equation of sphere is
x2+y2+z2−4x−6y−8z=0