x² + y² = 16.
x² + y² = 1.
x² + y² = 100.
x² + y² = 49.
x² + y² = 3.
x² + y² = 196.
The radius of the circle decreases when you make the circle smaller.
x2 + y2 =144
x² + y² = 1.
x² + y² = 100.
x² + y² = 225.
x2 + y2 = 400
x² + y² = 64.
x² + y² = 49.
x² + y² = 3.
x² + y² = 36.
x² + y² = 196.
The equation is: x2+y2 = radius2