#### Answer

(a) The center of the sphere is $(1,-2,-4)$
(b) The length of the radius of the sphere is $6$

#### Work Step by Step

We can write the general equation of a sphere:
$(x-a)^2+(y-b)^2+(z-c)^2 = r^2$
where $(a,b,c)$ is the center of the sphere and $r$ is the radius
The equation of the sphere is: $(x-1)^2+(y+2)^2+(z+4)^2 = 36$
(a) The center of the sphere is $(1,-2,-4)$
(b) The length of the radius of the sphere is $6$