[a-b]³怎么算?

[a-b]³怎么算?
[a-b]³怎么算?

[a-b]³怎么算?
(a-b)^3=(a-b)^2×（a-b）
=(a^2-2ab+b^2)(a-b)
=a^3-a^2b-2a^2b+2ab^2+ab^2-b^3
=a^3-b^3-3a^2b+3ab^2

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