d) x(x – 1)(x + 1) – (x − 3)(x^2 + 3x + 9).

d) x(x – 1)(x + 1) – (x − 3)(x² + 3x + 9)

= x[(x – 1)(x + 1)] ‒ (x³ ‒ 3³)

= x(x² ‒ 1) ‒ (x³ – 27)

= x³ ‒ x ‒ x³ + 27

= (x³ ‒ x³) ‒ x + 27

= 27 ‒ x.