Ta có: \(a\left(b-c\right)^3+b\left(c-a\right)^3+c\left(a-b\right)^3\)
\(=a\left(b^3-3b^2c+3bc^2-c^3\right)+b\left(c^3-3c^2a+3ca^2-a^3\right)+c\left(a^3-3a^2b+3ab^2-b^3\right)\)
\(=ab^3-3ab^2c+3abc^2-ac^3+bc^3-3abc^2+3a^2bc-a^3b+a^3c-3a^2bc+3ab^2c-cb^3\)
\(=ab^3-ac^3+bc^3-a^3b+a^3c-cb^3\)
\(=ab^3-a^3c-cb^3+bc^3-ac^3-a^3b\)
Tới đây bí rồi