Question

立方和和立方差 就是a+b的完全立方和a+b的完全立方

Answer 1

(a+b)^3

=(a+b)(a+b)(a+b)

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

=a^3+3a^2b+3ab^2+b^3

(a-b)^3

=(a-b)(a-b)(a-b)

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

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