If the center is (0, 0), then there is no side to side or up or down motion. The center is at the origin. The standard form of a circle is (x-h)^2 + (y-k)^2 = r^2. Your h and your k are both 0's, so just fill in and square the radius:
x^2 + y^2 = 64
Your answer is c.) 225. it is the only one that is not a decimal, this is more, not less
The answer to your question is k and m are both 9
You will need to subtract if u are taking 15% off