(a+b+c)(a2乗+b2乗+c2乗-ab-ac-bc)+3abc

(a+b+c)(a2乗+b2乗+c2乗-ab-ac-bc)+3abc

(a+b+c)(a^2+b^2+c^2-ab-ac-bc)+3abc=(a+b+c)(a^2+b^2+2ab-ac-bc+c^2)-3ab(a+b+c)+3abc=(a+b+c)[(a+b)^2-(a+b)c+c^2]-3ab(a+b+c)+3abc=[(a+b)^3+c^3]-(3a^2b+3ab^2+3abc)+3abc=[(a+b)^3a^2b-3ab^2]+c^3a bc+3abc=a^3+b^3+c^3