x2 + y2 = 25
A circle with centre (xo, yo) and radius r has equation:
(x - xo)2 + (y - yo)2 = r2
So with centre the origin (0, 0) and radius 5 cm, the circle has equation:
(x - 0)2 + (y - 0)2 = 52
⇒ x2 + y2 = 25
x2 + y2 =144
x² + y² = 64.
x2 + y2 = 400
x² + y² = 225.
x2 + y2 = 25
The radius of the circle decreases when you make the circle smaller.
x2 + y2 =144
x² + y² = 1.
x² + y² = 64.
x² + y² = 16.
x2 + y2 = 400
x² + y² = 100.
x² + y² = 225.
x² + y² = 49.
x² + y² = 3.
x² + y² = 196.
x² + y² = 36.