Question

Answer 1

a^3+b^3+c^3=3abc

=>(a+b)^3+c^3-3ab(a+b)-3abc=0

=>(a+b+c)(a^2+b^2+c^2-ab-bc-ac)=0

=>a^2+b^2+c^2-ab-bc-ac=0

=>2a^2+2b^2+2c^2-2ab-2bc-2ac=0

=>(a-b)^2+(b-c)^2+(a-c)^2=0

=>a=b=c

\(M=\left(a+a\right)\left(a+a\right)\left(a+a\right)-a^3=7a^3\)