Answer
$(x+1)^2+(y-3)^2=5$
Work Step by Step
Step 1. Find the distance between the two points: $d=\sqrt {(1-(-3))^2+(4-2)^2}=2\sqrt 5$
Step 2. A circle of least radius will have the two points at ends of a diameter, thus $r=d/2=\sqrt 5$
Step 3. The middle point (center of the circle) between the two endpoints can be found as $(\frac{1-3}{2},\frac{4+2}{2})$ or $(-1,3)$
Step 4. The equation can be written as: $(x+1)^2+(y-3)^2=5$
