Question 372552
Draw a line from ({{{-3}}},{{{-6}}}) to ({{{9}}},{{{-6}}}).
The midpoint of that line is ({{{3}}},{{{-6}}}).
Since the distance from the midpoint to ({{{3,{{{0) is equal to distance from midpoint to ({{{-3}}},{{{-6}}}) and ({{{9}}},{{{-6}}}), it is the center of the circle.
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{{{drawing(300,300,-6,10,-8,8,
circle(-3,-6,0.3),
circle(9,-6,0.3),
circle(3,0,0.3),
grid(1),
blue(line(-3,-6,9,-6)),
blue(line(3,-6,3,0)),
circle(3,-6,0.3),
graph(300,300,-6,10,-8,8))}}}
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The radius is the distance from the center to any of the points and equals {{{6}}} units.
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{{{(x-3)^2+(y+6)^2=36}}}