Question 901892
Find the distance between the two points using the distance formula. 
That distance is the diameter of the circle.
The radius is one half of that value.
{{{D^2=(1-15)^2+(-7-3)^2}}}
{{{D^2=(-14)^2+(-10)^2}}}
{{{D^2=196+100}}}
{{{D^2=296}}}
{{{D=sqrt(296)}}}
{{{D=2*sqrt(74)}}}
So then,
{{{R=(1/2)D}}}
{{{R=sqrt(74)}}}