Answer:
C and D
Step-by-step explanation:
The equation of a circle is
(x - h)² + (y - k)² = r² where (h,k) is the center, and r is the radius
Plug in what you were given, and simplify...
(x - 0)² + (y - (-8))² = 9²
x² + (y + 8)² = 81
This is answer C.
We can get answer D by foiling out (y + 8)² and simpligying...
x² + y² + 16y + 64 = 81
x² + y² + 16y = 17 (subtract 64 from both sides)