maths question x1(f.2)

a^3 -b^3 + 3ab^2 -3a^2 b
=(a-b)(a^2+ab+b^2)+3ab(b-a)
=(a-b)(a^2+ab+b^2-3ab)
=(a-b)(a^2-2ab+b^2)
=(a-b)(a-b)^2
=(a-b)^3

2006-12-16 23:32:12 補充：
如果用factorization..(a-b)^3都未out-see..因為呢條數..f.4 o既a-maths係有一條式..就即計到..

(a-b)^3
This question should not appear in f.2 sysllabus.