A student factorises x2+4x−12 as (x−2)(x+6). Which of the following statements is correct?
a) The factorisation is correct, but the roots should be x=−2,6.
b) The factorisation and the roots x=2,−6 are both correct.
c) The factorisation is incorrect because both brackets should have '+': (x+2)(x+6).
d) The factorisation is incorrect because the product of the constant terms is +12, not −12.