Answer
center $(2,0,-1)$, radius $r=\frac{3\sqrt 2}{2}$
Work Step by Step
$2x^2+2y^2+2z^2-8x+4z=-1$,
$2(x^2-4x+4)+2(y)^2+2(z^2+2z+1)=-1+8+2$,
$2(x-2)^2+2(y)^2+2(z+1)^2=9$,
$(x-2)^2+(y)^2+(z+1)^2=\frac{9}{2}$,
Thus center $(2,0,-1)$, radius $r=\frac{3\sqrt 2}{2}$
