The polynomial g(x)=x4+x3+2x2+4x−8 can be expressed as a product of two linear factors and one quadratic factor that cannot be split further over the real numbers. Which of the following gives this complete factorisation?
a) (x−1)(x−2)(x2+4)
b) (x−1)(x+2)(x2+4)
c) (x−1)(x+2)(x2−4)
d) (x−1)(x+2)(x2+2x+4)