Calculus 8th Edition

$x^{2} + y^{2} + z^{2} - 2x - 4y + 8z = 15$ $x^{2} - 2x + y^{2} - 4y + z^{2} + 8z = 15$ $x^{2} - 2x +1 + y^{2} - 4y +4 + z^{2} + 8z + 16 = 15 + 1 + 4 + 16$ $(x-1)^{2} + (y-2)^{2} + (z+4)^{2} = 36$ This is indeed a sphere, the center is at (1, 2, -4) and the radius is 6