Hi, for the equation of a circle you first need to find the center;
midpoint = ((x1 + x2)/2, (y1 + y2)/2)
= (-3 + 7)/2, (2 + 4)/2)
= (2, 3)
Now that we have the center, we need the radius:
r = √(x1 - x2)2 + (y1 - y2)2
Let's use (2,3) for (x1,y1) and (7,4) for (x2,y2)
r = √(7-2)2 + (4-3)2
r = √25 + 1
r = √26
Now we can find the equation of circle with center (2,3) and radius √26
(x - 2)2 + (y - 3)2 = 26