Question

Write the equation of a circle with its center at (0, 0) and a radius of 3.

Answer 1

The answer is x^2 + y^2 = 9

For this problem, you should use the equation of circle:

(x - h) ^2 + (y - k)^2 = r^2

where (h,k) is the coordinates of the center
and r is radius

(x - 0) ^2 + (y - 0)^2 = 3^2

Therefore:

x^2 + y^2 = 9