The diameter is 12 units long. Their equation could be seen in y = 1, because it is a horizontal line. From x = - 7 to x = 0 is 7 units. From x = 0 to x = 5, is 5 units. 5 + 7 = 12. This means the radius is 6. We will use this later. If you need another way to find the radius, let me know. I can just use distance formula.
We will use these endpoints to find the center.
Midpoint =
=
=
= (- 1, 1)
This is the center.
The equation of a circle is (x - h)² + (y - k)² = radius² where (h, k) is the center.
Plug in our given information now.
(x + 1)² + (y - 1)² = 6²
(x + 1)² + (y - 1)² = 36 is your equation.