If–1 is a root of f(x), which of the following must be true?
O A factor of f(x) is (x - 1).
O A factor of f(x) is (x + 1).
O Both (x - 1) and (x + 1) are factors of f(x).
ONeither (x - 1) nor (x + 1) is a factor of f(x).