Write the equation of a circle that has a center at the origin and a radius with a length of 3 inches.

hello:

an equation of the circle Center at the A (a, b) and ridus : r is:

(x-a) ² + (y-b) ² = r²

in this exercice : a = 0 and b = 0 and r=3 (Center at the origin: A=O) is : x²+y² = 9