1. Using the Factor Theorem, which of the following is true?
a. f(x) = x2 – x² + x - 1; f(1) = 0, so x - 1 is a factor of f(x)
b. f(x) = x - x + x - 1; f(1) = 0, so x + 1 is a factor of f(x)
c. f(x) = x - x2 + x - 1; f(2) = 5, so x - 2 is a factor of f(x)
d. f(x) = x - x + x - 1;X-1 is a factor of f(x), so f(-1) = 0​