1. The problem statement, all variables and given/known data Find the radius and center for the sphere determined by the four points (3,2,-1), (5,-2,1), (-3,1,2), (0,2,4). Give the exact location of the center but approximate the radius to the nearest 0.1. 2. Relevant equations Equation of a sphere: x2 + y2 + z2 + Gx +Hy +Iz +J = 0 or C(h,k,l) (x-h)2 + (y-k)2 + (z-l)2 - r2 = 0 There's also a 5x5 matrix with the determinant equal to zero, but I have no idea how to use it (seen at line 29 here: http://mathworld.wolfram.com/Sphere.html). I believe this is beyond 12.1 in multivariable calculus. 3. The attempt at a solution I tried to use the determinant formula, but I got lost as I don't even know how to use it. Is there any other way? EDIT: Solved. Thank you.