i) a3 – a2b2 – ab + b3
= (a3 – a2b2) – (ab – b3)
= (a2 × a – a2 × b2) – (a × b – b × b2)
= a2(a – b2) – b(a – b2)
= (a – b2) (a2 – b)
ii) p2q – pr2 – pq + r2
= (p2q – pr2) – (pq – r2)
= (p × p × q – p × r × r) – (pq – r2)
= p(pq – r2) – (pq – r2)
= (p – 1) (pq – r2)