Answer
$3\sqrt{5}$ units
Work Step by Step
To find the distance between the two points, we use the distance formula:
$d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$
We plug in the points $(2,\ -3)$ and $(-1,3)$:
$d=\sqrt{(-1-2)^{2}+(3--3)^{2}}$
$=\sqrt{(-3)^{2}+6^{2}}$
$=\sqrt{9+36}$
$=\sqrt{45}$
$=\sqrt{9*5}$
$=3\sqrt{5}$
Thus the distance and hence the radius is $3\sqrt{5}$.
