Question

(a+b)的3次方、4次方怎么算?

Answer 1

(a+b)^3

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

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

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

(a+b)^4

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

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

=a^4+4a^3b^3+6a^2b^2+4ab^3+b^4