Cho

- Hướng dẫn giải

$M=a^3+b^3+c\left(a^2+b^2\right)-abc$

$\begin{array}{l}=a^3+b^3+a^{2}c+b^{2}c-abc\\ =\left(a^3+a^{2}c\right)+\left(b^3+b^{2}c\right)-abc\\ =a^2\left(a+c\right)+b^2\left(b+c\right)-abc\\ =a^2\left(-b\right)+b^2\left(-a\right)-abc\\ =-ab\left(a+b+c\right)\\ =0\end{array}$

Vậy M = 0