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