(x2 – x)2 – 8(x2 – x) + 12
= m2 – 8m + 12 …[Putting x2 – x = m]
= m2 – 6m – 2m + 12
= m(m – 6) – 2(m – 6)
= (m – 6)(m – 2)
= (x2 – x- 6) (x2 – x- 2) …[Replacing m = x2 -x]
= (x2 – 3x + 2x – 6) (x2 – 2x + x – 2)
= [x(x – 3) + 2(x – 3)] [x(x – 2) + 1 (x-2)]
= (x – 3) (x + 2) (x – 2) (x + 1)