Question

1-c^8

Answer 1

-1(c^8-1)=-1(c^4-1)(c^4+1)=-1(c^2-1)(c^2+1)(c^4+1)=-1(c-1)(c+1)(c^2+1)(c^4+1)

Answer 2

=(1+c^4)(1-c^4)
= (1-c^2)(1+c^2)(1+c^4)
= (1-c)(1+c)(1+c^2)(1+c^4)

Answer 3

ndog is correct, but some consider this to a slightly better form since it has fewer negative signs:
(1-c)(c+1)(c^2+1)(c^4+1)