Answer:
4
Step-by-step explanation:
The general equation of a circle with center (a, b) and radius r is given by the equation;
[tex](x-a)^{2}+(y-b)^{2}=r^{2}[/tex]
The constant in the right hand side of the equation is simply the square of the radius;
We have been given the following equation;
(x-3)^2 + (y+1)^2 = 16
Comparing this with the general equation above;
[tex]r^{2}=16\\\\r=\sqrt{16}=4[/tex]
