Answer
$(x-2)^2+(y+1)^2=16$
Work Step by Step
RECALL:
The standard form of the equation of a circle with a center of $(h, k)$ and a radius of $r$ units is:
$(x-h)^2 + (y-k)^2 = r^2$
Use the standard form above where $h=2$, $k=-1$, and $r=4$ to obtain:
$(x-2)^2 + [y-(-1)^2] =4^2
\\(x-2)^2+(y+1)^2=16$