Ta có : \(a+b+c=0\)
\(\Rightarrow\left\{{}\begin{matrix}a+b=-c\\a+c=-b\\b+c=-a\end{matrix}\right.\)
\(M=a.\left(-c\right).\left(-b\right)=abc\)
\(N=b.\left(-a\right).\left(-c\right)=abc\)
\(P=c.\left(-b\right).\left(-a\right)=abc\)
\(\Rightarrow M=N=P\)