α+β+γ=0
-(α+β)=γ
(α+β+γ)²=α²+β²+γ²+2βγ+2γα+2αβ=0
α²+β²+γ²-βγ-γα-αβ=-3(βγ+γα+αβ)=3(α²+β²+αβ)