Answer:
D
Step-by-step explanation:
The equation of a circle centred at the origin is
x² + y² = r² ( where r is the radius )
Here r = 15, thus
x² + y² = 15² , that is
x² + y² = 225 → D
d^4-8d^2+16
(d^2-4d)(d^2-4d)
(d-2)(d+2)(d-2)(d+2)
Option D is correct