The equation of a circle is given by the formula;
(x-h)² + (y-k)² = r²
r is the radius of the circle
(h,k) is the center of the circle
Smallest circle (Red circle)
r = 1
(h,k)= (0, 7)
substitute the values into the formular
(x - 0)² + (y-7)² = 1²
x²+ (y-7)² =1
Bigger circle (Blue circle)
r= 3 h=0 K=3
substitute the values into the formula
(x -0)² + (y-3)²= 3²
x² + (y-3)² = 9
Biggest circle ( Orange Circle)
r=5 h=0 K=-5
substitute the values into the formula and evaluate
(x-0)² + (y+5)² = 5²
x² +(y+5)² = 25