Hi!
The equation of a circle is (x – h)² + (y – k)² = r², with (h, k) being the center, r being the radius, and x + y being left as just x and y.
If the smallest circle has a radius of 3 units, then the next one is 7 units (4 units greater), and then the second largest 11 units, and then the largest 15. That means, for r in our equation, we're going to put in 15.
So we get:
(x – h)² + (y – k)² = 15², or
(x – h)² + (y – k)² = 225
The center of our circle is at (-4, 3). That means h = -4 and k = 3 in our equation. So let's substitute that in.
(x – (-4))² + (y – 3)² = 225
(x + 4)² + (y - 3)² = 225 is our final equation.
Hope this helped!
